When I did that section, here's our itinerary:
Overnight at Onion Valley trail head.
1. Long day to Center Basin creek
2. Center Basin creek to Wallace Creek
3. Wallace Creek to Whitney Summit
Ate a big meal, swam and loafed at Guitar Lk several hours.
(spent the night on top)
4. Out to Whitney Portal.
Day 1 and 2 were long, and I suffered from AMS (appetite loss) at the end of both days. By day 3, I was better.