E-Mail, IM and other stuff is nice to get reached, but unfortunately, it's also very time-consuming. Especially if E-Mail is (ab)used as a near-realtime communication system. In order to make it a bit more efficient, I'm changing my communication patterns a bit. I'll try to check mails in a "best-effort" manner in the future, so no guarantees, and the timing is going to be like this. From Monday to Friday, I'll try to check early in the morning (around 8-10) and once in the afternoon-early evening (15-18). IM presence will be reduced mostly to weekends and occasionally in the evening.
If there is something urgent, feel free to call me, or make an appointment. This is going to be much more effective than IM and E-Mail troubleshooting. For E-Mail, I actually analysed all my mail in the last year for "urgency". There is not a single one which would have required a <24 hour response time, and most of the time <48 would have been sufficient. As I'm much faster during batch-processing mail, I've opted in for this new policy -- which in turn should improve the answer quality :), so it's a win-win.
You shouldn't expect an answer at all on weekends, even though I'll try to check mail. I'm also no friend of exceptions, so if there is a deadline on Sunday -- bad luck. The latter worked out very nicely so far, we managed for instance to have a paper finished several days in advance of the deadline, it's all a matter of planning.