I'm skeptical of any bikes becoming a collector item in any real degree aside from its sentimental value to the original owner. Unlike a car, there is always a fit issue with any other owner, and then there is the problem with leaving it original versus upgrading it to make it more enjoyable to ride.
For example, I am always watching Ebay and other sites lusting after a late 70's early 80s Masi GC--hankering back to those of us older folks who caught the bug watching "Breaking Away." I have a friend with an old steel Pinarello that I am always admiring and threatening to steel from his garage for a spin. You can still buy and restore a bike pretty cheaply. I haven't seen anything go for a crazy price.
For a nice US guideline, The Seven Eleven bikes of the 80s also have a particular appeal to folks of a certain age. For example, Frankie Andreu's '89 7-11 team bike was listed for sale at around $6500--pricey--but it is not going to make anyone rich.
Given the doping history of Postal, I doubt that the '02 Postal version Trek is going to be particularly valuable. If it was ridden by an actual team member, then it might be of interest to certain collectors, but even then, there just isn't a big market.
If you like riding them, then ride the [censored] out of them and have fun. If they have less than 200 miles on both of them, particularly a 2002 USPS bike, then you are doing something wrong. My guideline is one season. If I haven't ridden a bike with any frequency for more than a season, than its just taking up space. Unless you are Robin Williams and your estate is auctioning bikes off for charity, they are just taking up space. As far as I'm concerned, it you really have less than 200 miles on both of them, you've already answered your question, there must be something you like riding a whole lot more and I'd sell or donate both of them. If I really do "love" a bike, I'm riding it more than 200 miles within a few weeks of owning it.
I am a big fan of the N + 1 philosophy of bikes. The proper amount of bikes should be the bikes you own and ride regularly, plus one bike you don't own that you lust after to ride. If you really love to ride. . . as opposed to collect, then you already need to own a road bike, a beater road bike for crappy weather, a cyclocross bike, a full suspension mountain bike, a fixed gear, a hardtail mt bike, and a city (beach) cruiser. My plus one is currently a fat bike. That's seven bikes plus one, which means, I don't have the luxury of keeping another two road bikes I rarely ride. I'd also like to buy a tri or time trial bike soon for duatholons in the spring, so I'm really down 2 from the optimum. And I would like to have a 29er and maybe an e-bike just for [censored] and giggles.If I own anyone of them for more than a few months and don't put a few hundred miles on them, then I'm getting rid of it, and I wouldn't say that I "love" it.