What a question, hOughy!
I'd travel a lot further to see something than I would to not see it!!!
Unless I'm just going to do some lunar imaging (because the moon is up) I routinely drive about 22ks each way to get to my viewing site (dark). Really I suppose I'm getting away from the street lights over my yard and the lights of the town and factories...
It depends too on what's important, what you are seeing or the journey? I've travelled 350ks each way in the one day to have a look at the Parkes Radio Telescope, but it was the cruising country roads on the BM that was the important bit...
I should've travelled just 50 or so ks to Bathurst the other day for the Mercury Transit but I didn't know it was clear there did I? 20/20 hindsight... don't you love it?

If I could've known that 100ks away would definitely be clear and here wasn't, I would go... trouble is that element of uncertainty!
Al.