Therein lies your mistake. Any admin that's been around even a short while knows to NEVER MAKE CHANGES ON A FRIDAY! :P
Yepp, right. Also, don't release updates on fridays.
But to be serious: We are a small team, and experience has shown that we can get away with one admin day every two weeks, plus a total of perhaps an hour per week for the little problems of the non-nerds in the team. (My boss is still amazed that the machines can mostly maintain themselves. I'm just too lazy for routine jobs.)
I prefer to start late and go home late, so I can shut down systems on a friday afternoon usually without disturbing anyone. And if I really mess up stuff, I have two days to clean up before the systems have to be up and running again. (That never happened so far.)
From time to time, we change larger parts of our infrastructure (new cables, new servers, changes to the electrical system, new PBX). That typically happens on a week-end in exchange for a few extra free days.
Also, switching to "admin mode" helps getting a different perspective on development problems - like leaving the office for a short walk, but for a full eight hours.