As others have stated, your tire pressure will always go up on any vehicle once you start driving, even in the winter as normal rolling resistance creates friction and therefore heat.
What is key, is the COLD tire pressure. You can actually go all the way up to the tire manufacturer's MAX PSI without any issues of tire safety (even with them warming up when driving), needless to say the higher you go the stiffer the ride will be, which isn't always a bad thing.
I had a 2008 Prius that I bought new and kept the tire pressure year round at the tire posted MAX PSI cold, I think it was 51 PSI if I recall now. I drove it like that for 4 years, had perfect tire wear (measured regularly with a tire depth gauge) and it greatly improved my fuel economy, thus the point of the Prius.
Normally, on my other vehicles, I run about 1-2 PSI higher to get better fuel economy and better handling on the road. The pressure indicated on the door jam is a 'recommendation' from the car manufacturer for the greater overall masses to provide a nice ride and handling baseline.
There is no harm in bumping it up a couple PSI and seeing what it does for your mileage, just stay within the MAX PSI rated on the tire.
I'm looking at getting my first Acura, an RDX and as I do allot of highway driving will be adjusting the PSI up a couple PSI for better fuel economy and tire wear.