I did try a slightly different pattern of using up my time off in lieu of evening classes. Previously I was working until 5.00 pm on Thursday and then trying to go home just after lunch on Friday, taking the time in one block. (Though often I'd get caught up in stuff and end up working till 5.00 anyway.) However, this week, I left as soon as I could on Thursday (4.00 pm) and then left just after 3.00 on Friday. As a result, I feel much less shattered today and might get more useful stuff done.
If this genuinely works and wasn't just a one off, then it might increase my productivity all round, including writing. Previously Saturdays were a write off when I just crashed, read LJ and Usenet, fiddled around doing nothing in particular and then (having done Catching Up With Housework on Sunday), ended up spending Monday rushing round like a mad thing getting ready for work on Tuesday.