I go every year. I am like a kid getting the Sears catalog when I am there. It is great visiting with the vendors that you have relationships with and meeting new ones. You just cannot beat the personal touch. For obscure items and one offs, this may be your only chance to get access to the info. My buddy Darin Morgan will be doing two seminars on cylinder heads, if you have not heard Darin speak, it is well worth your time.
Yes, you do need good knees for PRI, I usually walk 12,000 to 16,000 steps per day when I am there.