Three years for ST, up to seven for LT.
I overinflate mine by 10% for storage, park trailer on pressure treat boards, and keep them covered.
Still wouldn’t change above (except that you couldn’t give me ST. It’s the rating, not the manufacturer or country of origin):
1) The risk associated with being on the side of the highway is too great.
2). The money to fix the TT after tread separation damage ($7-8k) buys a lifetime of the most expensive tires and then some.
3). Add shock absorbers if TT doesn’t have them. No reason to force the tires to do extra work, and TT road manners are improved.
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