I don't ride like you do CampyBob so I only carry one extra pair of tires in reserve, and I only order another pair if I find a really low price and it's too good to pass up or wait till I use that spare reserve pair then start looking for deals, it's not uncommon for me not to have any tires in reserve before I start looking for tires. I have other bikes with tires so if I really needed to I could take a tire off one of the bikes I don't use much and put them on the bike I need a tire for, if that happens I usually simply ride another bike with good tires till I get a tire(s) for my main bike.
Right now I have a set of Roubaix Pro tires in storage I got when they had the sale so I'll probably be good for at least another year and probably two.
I don't know if I buy into the aging tire thing you do CampyBob, because tires are not wine, as they age they are actually deteriorating. Plus any tire you buy didn't come straight from the factory directly to you, they were first stored in a factory warehouse in say Taiwan for who knows how long before a warehouse in the US asks for restocking, then sent by truck to a dock area where they are put into a shipping container and could set on that dock for a week to a month all the while baking in a hot container, then loaded on a ship that could take between 15 to 40 days to get to say California again baking in the sun, it then sets on the dock for a while till it's loaded on a truck or train and taken to an area where it will be transferred again to a truck and taken to a warehouse will it will set till an order calls for it to be picked. So really when you order a set of tires they could be already a year old before you get them! In fact I think closeout sales on tires are tires that are right around 1 1/2 to 2 years old.
Automotive tires the federal government is VERY concerned about tires that have sat around too long before being sold so they now put date codes on tires and if a tire is not sold by a certain date that tire is sent back.
You can read this about car tires:
https://www.utires.com/articles/after-how-many-years-should-i-change-my-tires/
I once followed a friend home from Illinois to NE Indiana who was driving a 1962 Ford T-Bird that had the original tires from the factory! the tires were cracked but he decided to drive the car home anyways, we made it home without a tire failure.
You can read about this even with motorcycle tires, see:
https://www.motorcyclistonline.com/do-motorcycle-tires-have-shelf-life#page-3
Of course car/MC tires are designed to go a lot faster than a bike tire will and thus the heat from going faster can be an accident waiting to happen if the tires are too old, but the point of those articles is that tires do age.
Here is something about bike tires:
https://www.velonews.com/2014/04/bi...hnical-faq-taking-care-of-unused-tires_325651
Keep in mind that car tires and motorcycle tires are constructed far better than bicycle tires thus I seriously doubt that a bike tire should be aged. However if you're using ultra expensive silk cased tubular tires there was something I heard many years ago that the silk did need to be aged but it was a balancing act because the rubber was also aging which wasn't good for the rubber. There was also something I read some years back that some pro cycling team coach guy would store only tubulars (I can't recall if those were silk or not, I think so) for 5 to 7 years before using them BUT he stored them in a wine cellar with 40 psi in them which meant he had to constantly go down into the cellar every day and keep those tires at 40 psi, but he said that was only necessary with those type of tubulars and not necessary and unadvisable for clinchers. But keep in mind that this guy had no science behind what he was doing, it was something he thought should be done but I think he was wrong! Because as tires age the rubber becomes harder not more supple, even natural rubber used in high end tubulars will become hard after a long period of time, maybe the silk became more supple? which I can't see silk going through any changes encase in natural rubber or not encased and just setting out in the open but we were told that, but the rubber getting harder ruined whatever improvement the silk had to offer by aging. The common thing now is to age tubulars inflated in a dry cool place for 6 months but that's due to the natural rubber used in a lot of tubulars, synthetic rubber used in all clinchers and some tubulars do not require any aging and in fact will only harden with age. Natural rubber when fresh is sticky so it picks up more road debris which can cause more flats, but after aging roughly 6 months the rubber hardens (and continues to do so but that becomes a disadvantage the more time goes by), however I believe that with shipping and storage times those 6 months are already used by the time you get the tire so aging them any further is actually going backwards in helping the tire.
By the way, cheaper tubulars that use cotton I never heard of any advantage aging those.
Now having said all of that, I did mention I have a pair of tires that may not be used for a year, it's not that I'm aging them, it's just that I don't believe that storing tires makes such a dramatic change to the tire that I'm endangering myself by doing so. I have a pair of tires that came off of a 1984 Fuji Club that came with the bike when it was new (the bike and tires only saw 5 miles since it was new till I bought it about 6 or 7 years ago) and I have full confidence in those tires that I could ride them anywhere I wanted to, the only reason I took them off is because the flat resistance in those older tires were non existent unlike those made today, but I did ride on those tires for about 25 miles before I got a set of tires to replace them with. Even after all those years in storage those tires do not have one crack on them anywhere, and they didn't act "slick" from having hardened aged rubber, nor do they even feel hard or brittle. I have another tire that I got around the late 90's that for years just sat in my seat bag as a spare and now sits in my tool box with my Spesh tires, I took it out just today because of this conversation and looked at it closely and found no cracks in it either and those saw about 500 miles of use before becoming my spare, they also don't feel hard or brittle. So really, maybe the rubber on those older tires got a bit harder then they were when new but that didn't make them unrideable, and unless I was racing or descending fast winding mountain roads the harder rubber won't mean anything.
So at the end of the day, if you want to age them because that's what you've been doing for 40 years go ahead you're not riding on dangerous tires, if you decide to use them immediately after purchase go ahead you won't notice any difference anyways. Synthetic rubber just doesn't go through a lot of changes even after a few years.