I'd do it. I often work longer than my official hours anyway, so the extra hour wouldn't be a big deal. But I can understand not doing it to enjoy the quiet time at work. We have a rota to cover having the office open with a skeleton staff on Saturdays., then we get a day off in lieu. As Saturday is always really quiet, I can catch up on a lot, then, and then if I take a Friday or a Monday off I get the relaxation of a long weekend.