You do need to plan time off in this job; otherwise you just end up feeling burnt out and taking days off here, there, and everywhere; not working a full day either. You'll find that with a PLANNED week off, you'll work harder towards that time off - enjoy the time off - and find your batteries charged more after it.
I've just really recently learnt this from experience, after five years of working without a proper planned break of at least a week off; with nothing to do with window cleaning.
Unfortunately I spent my week off DIYing, but hey, a change is as good as a rest.