Time vs. Miles

Hi, got a situation that has probably happened to at least one of you before.

I finally got around to tinkering with my ride and noticed my tires were severly underinflated, so of course I put air in them. Now to my question:

I used to do my normal ride in 2 hr 30 minutes, but now can do it in 2 hours. So if I just go by miles, but at a faster pace will my 1) Cardio and 2) calories be pretty close to what it used to be or do I have to be on the bike at least 2 hrs 30 minutes just to "maintain" where I am at physically? With soft tires my mph was 13.3 and properly inflated tires I avg 14.5 mph.

Some people on say the body only measures time on the bike and not miles. What's the more scientific evidence?

Time at a certain HR is going to be your benchmark for calories burned. Miles can become easier with time and keep you out of your target HR zone - go by time in the saddle and crank those miles up!

Physically if you need to move 1Kg of mass by 1 metre,
you need to spend 1 Joule of energy.
(this is secondary school physic stuff)
(and in the perfect environment etc etc...)
But if you are out there battle against the wind for longer time,
then of course you will spend more energy.

How many miles can you do in 2h30m?