In a weird paradoxical sort of way, not starting to tear something up for a scheduled rebuild actually makes it more available for short-notice emergency use.
Well, in most cases, you'd be right, but for one little problem--it's a bit more difficult to refuel a nuke than it is a conventional asset, and that's what the Lincoln and GW were going in for in addition to complex overhaul. Once that reactor plant (plants, plural--Nimitz-class have two A4W plants) is Xenon-precluded, you're DONE. Dumping a hunk of Uranium in the core just ain't gonna do it anymore.
I've no idea what the core life in EFPH (Effective Full Power Hours) for an A4W plant would be, but you've got to consider that the TR is currently in RCOH (since 2010) and was about 24-25 years old when she hit the drydock, and Lincoln and GW are 24 and 21 years old, respectively, they're due.