While it works to decide to check email only 2-3 times a day, it doesn't work so well with IM. IM discussions are typically much faster and there's a big risk you miss out on giving your POV before everyone has moved on, if you only check it every now and then.

If everyone moved on, was it really important to give your input anyway?

With IM you can turn it off if you need to focus, and turn it on when you are doing busy work anyway.