There's a basic flaw in that premise. Elite athletes maintain their ability to play at an elite level by playing at an elite level. In other words, if Webber is only used in critical cases, there is no guarantee he'll be able to perform in critical cases. You don't keep a race horse in the barn all year and expect him to come out and win the Kentucky Derby.
It's as simple as "use it or lose it" and we see it all the time. Webber will, most likely, take a game off here and there the rest of his career. I'm perfectly happy with that. When he plays, he has to PLAY.