It's not just how far you can go in one hit that makes a big tank worth while. I use my (30l) Adv to commute to work. It's only 30 miles or so a day so that means if I just use it for work then it's 8 days between fill-ups. I used to have an 1100S which did 110 between fill-ups, or 3-4 days. Just saves a bit of faffing about at petrol stations either to or from work.
I'd like to think that the big tank means I can cross the Gobi Desert in one hit if the desire strikes me, but I don't think that's going to happen this side of a Lottery win...