Play SNGs on the side ? Listen to soothing classical music ? Take up gardening ? Seriously, there's no real answer since you cannot do anything but play once you get 4 hours in and you should be even more focused because of your invested time.
Maybe donkaments are not for you. I know that after playing a deepstack, where I was def. +EV due to being able to play postflop, that I don't like spending 8 hours stealing and restealing even though I have an edge. Just not worth it since it takes forever to complete.