Your 60# bow will be just fine----Sit in a tree stand for 2 hours in -25 degree weather and then crank it back sitting down.You will be glad its set at 60,maybe even 55 lbs might sound better at that particular time.

My bow is set at 70# and isn't a problem during practice sessions in the warm weather or indoor shooting.Hunting season its down to around 65#'s and its comfortable.
Turn your bow up a bit for practice.You will develope more muscle,and a bit before hunting season crank her back down to 60.It will feel a whole lot easier to pull back being accustomed to 65 or more pounds.