Tires always lose air in storage is this normal?

Some good responses to this. I will say the tt is usually stored for 3 or 4 weeks and I always pick it up in the evening when I would guess the temp is 60-70 degrees. I will have to try measuring the psi at different times of the day. Also I agree that the nitrogen fill is truly the latest gimmick in the industry, the majority of the atmosphere is already nitrogen so I cannot see how this would make a difference.