The problem is that MX and airline management are using the MEL these days to NOT have to fix things, until they are forced to. 10 day deferral? Perfect, let's let them fly around for 9 days and then we will get around to it. The MEL was designed to get the airplane back to where MX can be performed, not let the airline run around for days doing turns from a MX base.

When I was at Comair they wouldn't fix Lavs or APU's in CVG because they wanted the plane to fly all day until it got line MX on the overnight. I had to scream many times to get them to fix a lav on a CVG-NAS-CVG turn, or threaten to refuse the plane.

Captain's Authority is just that. Use it when it is safe and prudent.