Is it possible your approach to instant messaging is wrong?
Can you suggest a better way to use IM that doesn't require me to respond quickly?
I'm fine with IM for sending over quick URL's, etc while doing a live debug or something. But if you just have a "quick question", email me if not urgent or come to my cube if it is. If you are located far away, call me. Both email and phone are more efficient for simple questions. IM is in the unhappy place where it's worse than both.
If they expected a response within an hour and didn't get it, they can call me or physically come to me.
I've told two of my bosses while being interviewed: Assume I'll check email only 3 times a day. Is that workable?
No one says "No" (even though it may not be workable).
One of my bosses actually suggested to me that I should have "office hours" and be available in those hours, and simply not respond all other hours.
It all depends on the need of the job. And most engineering/SW jobs do not need you to "be available to respond within an hour" for any request.
My boss who suggested office hours wouldn't want to hire someone with your view.
Further, you have no clue what my policy is regarding instant messaging, don't lash out at me because you're feeling vulnerable.
Whatever provides less cognitive dissonance, I guess?