Tires always lose air in storage is this normal?

All rubber tires and/or tubes lose air constantly, but very slowly. ALL.

Long term inactivity is the worst possible thing for mounted tires. Read up on OEM's recommending airing up 25%-ish over max cold for long term storage. It helps prevent permanent flat spots.

No tubless tire makes a perfect seal with a rim. Same goes with valve stems. If it really troubles you, install tubes.

My experience has been that it depends on how long it's been sitting in storage. If just a couple weeks, I barely lose anything...Over winter, it may drop about 10psi.

They will lose air sitting and they will show less pressure on a cold day versus a warm day.

Mine don't lose that much. But they do lose some sitting around. And don't fall for that nitrogen thing. Mine came filled with Nitrogen. They still lost air waiting on the next trip.