Monroe air shocks

Every Monroe ones I've got for mopar cars say 80-150 psi .

But also one gotten 100 in them and they leak down over few weeks . And it's not the nuts or o rings as I've checked and re checked many times and had a shop check too . They just can't hold the pressure . They don't go flat but can't seem to handle 100 psi they leak down to like 75 and stop