Well after looking at the map, I know where the last days' route runs, I've ridden it all before. I'd like to get a GPS, but like you said, the GPS costs less then a set of tires, and guess what the bike needs...(a set of tires)
So regardless of whether I can afford a GPS or not, the last days route is engraved in my memory, so I can do it with out a GPS. It is on my list of things to buy.
I'd just like to meet up with part of the group so I could ride along insted of by myself.