I switch them out of the lighter guns when I see them getting lazy with their fundamentals. By lighter I mean 7lbs bare so not super light.
That's what I'm getting at... a regular, hunting weight rifle in 6.5CM is going to have more recoil than what is ideal for building good marksmanship skills. A braked or suppressed 12-15 lb rifle clamped in a tripod is a different animal altogether.