Thanks for your feedback. I'm reluctant to add preemptive income calculation tooltips, as the game already has various "guidance" mechanisms in place, and adding something this might remove strategy from the game and be received negatively by others. I'll think about adding an FAQ section to potentially clear up any ambiguities.
Regarding prestiging before going to bed, I'd recommend strategizing based on how much time you know you'd have available to play. If you're going to bed soon and don't believe you can get your income/sec back to what it was prior to prestiging before then, it's best to wait until the next day.