Half an hour; i don't like travelling long distances as i've heard it raise the stress rate and chances of the new fish not settling in well and becomming sick. I try to get my fish from the lfs, into my tank and acclimatized within 2hrs of purchase.
Mum and i took the car and went on a Fish Store shake down! LOl, we did it for the whole saturday, so id say it was quite a distance. But to my absolute fav lfs its about 1hour 20mins.
I think my furthest lfs is about 45 mins drive away.
I always make sure that the fish are the last things I buy from there as it can sometimes take a while to get off the car park (store is within a busy garden centre)
my fav LFS is only a 10 minute walk from my house or a 2 minute drive, but the other good LFS is a 15 minute round trip. we only have one other on the island and thats £30 minute round trip from my house.