[kirbwarrior]

I don't think I've ever had a time-travel heavy campaign (and I do want to try it) but it's definitely come up a lot as a one time thing in campaigns. Because I have a lot of control over how it can and will work, I can usually know ahead of time if and what the players will do if time travel comes up and retroactively change things if necessary. And that's assuming they travel back to where they left from. Basically, it just requires knowing enough of what is going on in the setting, figuring out how much needs to be changed, then how much you actually want changed.

I also have a pretty simple rule most of the time with time manipulation; No traveling to the past. Time goes forward. Consequently, you also can't see the future because information would be traveling to the past. Mind, that probably skirts the question for the exact reason I came up with it.

However, my big thought on time travel in general (not just roleplaying) is that I don't think paradox is a real thing and only something that is set up in hypothetical situations (or similar such as in the artificial system of math). Any system of time travel that would actually work both wouldn't have paradox and would likely be difficult, inconvenient, and limited in some manner. It would take a lot of planning ahead of time (something I'd do well before even telling the players about the campaign idea). But also, playing fast and loose with it and might do something silly like Chrono Trigger's approach to time travel which basically amounts to "don't let logic get in the way of fun".