Your old lens may have just needed a CLA n all would have been good again.

Also these lenses like to be excersized every now n again to keep em in working good order. If you are storing for a long period of time say a few months leave it uncocked as others already recomended. On n off camera makes no difference. Store your lenses n zip loc bags with a small packet of silica to keep moisture under control.

BTW why a 90 in place of a 65? I'd rather have the 65.

Good luck with your new to you camera n burn lots of film.. so lets see some pics now?