fhtpdw20, I have a schedule similar to yours. I just came back from DL this past weekend. I agree with the PP posters about taking the earlier flights going out. The direct flights are getting more and more expensive (at least out of PHL). I like SW and AT, and direct flights to California are pretty much non-existent on these two (2) airlines.
Going out I was fine, and got there early enough to do quite a bit before getting tired out. On the way back with the three (3) hour time difference, I really felt it the next day. I was so tired the next day after I returned home, I slept quite a bit of the day away. I think next time I will leave on an early morning flight instead of mid afternoon.