Steve,
I regularly hike to 10K (Mt. Baldy) and did San Gorgonio (11,500) twice before coming to Whitney, once via Vivian Creek and once via the South Fork loop. The South Fork loop is really good training for MW because it's 24.5 miles.
For training, and just general masochism, I also hiked up Baldy from Mt. Baldy Village which is a real grind (5,800' elevation gain in 6.5 miles), then down the Devil's Backbone trail to the Baldy ski area, over the 3 T's trail (which goes up and down 3 mountains) and out Icehouse Canyon trail. That's about 19.5 miles and beaucoup elevation gain and loss.
(I see you're in the Fresno area so these points might not mean much to you but people on the board from S. Cali will recognize them.)
Last summer I did a 14er in Colorado with no trouble at all, then came back to California and did MW but it was hard for me.
I think I handle the 14K altitude OK. It's the combination of altitude plus the long, hard trail that wiped me out and tells me I should consider Whitney as something I used to be able to do but not any more. I came too close to wiping out this time to want to do it again.
Anyway, I've got a lifetime record for MW of 5 summits in 8 tries.
