I was recently looking at this question, which seems to argue that FTL travel within the existing laws of physics can risk resulting in the destruction of half the universe. (Specifically, bad things occur when anything moving FTL hits anything else).
So, say you've handwaved this issue to allow for less dangerous FTL travel, by entering a separate hyperspace dimension where the rules are different, or whatever else. But say this mode of FTL is only possible under certain circumstances, or perhaps your handwavium drive is broken.
Have you noticed how in space opera when the "hyperdrive" breaks, somehow the heroes still manage to get from here to there in a reasonable amount of time? "Slower" maybe, but they still usually make it to "the nearest inhabited star system." Basically, if we don't want to risk wiping out large portions of the universe, how feasible is this?
In a situation where you cannot use your normal "safe" mode of FTL, how fast can you travel without risking an unacceptable "universe destroying" potential? The speed of light? Slightly slower? And following these guidelines, how long will it take you to go anywhere? How long to get to Pluto from Earth, or to Alpha Centauri? Would the valiant Captain be dead before he ever arrived at the nearest hyperdrive repair facility?