When I fill mine up I go to 40 PSI.

How long will it take for them to fall to 35?

Does it depend on how or how much I drive.
Temp?

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.

It probably varies but mine seems to drop about 1 PSI a week. I usually check mine every 3-4 weeks. I keep them at 40-41 PSI.

I check mine weekly and they're usually 1-2lb off. Sometimes no change for weeks.

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT

They should not go down except for changes in temperature.

If you have them all set at the same pressure (using an air gauge), they should all fluctuate in unison. If one is down more than the others, it has a leak somewhere.

There are far too many variables at work to state the answer for your case. All you can do is check them periodically- each fillup.

And find the stations near you that have free air, or keep a supply of quarters. Exxon usually has free air&water