for me if it were mine, I would inspect it and possibly keep it for a few more years… but if needed it would only be a spare to get to the next tire shop then back into the rack… I have used tires on the ground for much more than 7 years many times before…
but I could never recommend that to you or anyone else because I don’t know anything about the tire how it was maintained for seven years even though it was never used, or even if it is really 7 years old by the date code, no matter the trailer might be 7 years in your position…