My pick would have to be the A Whole Nother Story trilogy, in which (spoiler warning) you can only travel back in time. But because time is in a loop of sorts, if you go before the beginning of time, you will be at the end of time. From there you can go back to any time you want to. And time paradoxes cannot be produced. Plus, your memories from the previous timeline exist as well as the memories from the new one.
Aaand, having read the books and listened to the radio serieses so many time (I read the first book just before the official publication date, as a friend had got hold of an advance copy) it has only just occured to me that that is exactly what happened to Ford and Arthur. Though whether humankind as descended from the B-Ark crowd has ever managed the more responsible life-form bit is very much open to debate.
I also, given this topic, love the time paradox part of how they eventually get rescued by Zaphod by waving down a purely potential ship with Arthur’s towel.