I noticed that Delly played every minute of the SC game on Saturday and he is again leading the WCC in minutes played by a substantial margin, and guess who no. 4 and 5 on the list?  Holt and Jones.
I agree that averaging 36 vs 31 minutes should not be wearing them out, but I think the higher minutes increases the chances of getting various dings and injuries over the season and does not allow for recovery from injury.  Look at Mickey and Rob last least year towards the end playing many minutes in many games while hurt.  
I see why Randy plays Delly, Steve and Rob so much - the production falls off dramatically when they are not in the game.