The normal charity rides around here have rest stops every 10 miles or so. If it's hot and you're just carrying one or two bottles, you may stop at every one. If you're in North-East England, you may not appreciate what "hot" is. With a camelbak, you can stretch that to 30-40 miles when it's hot. But I digress...

Personally, I find it a lot more fun to ride with other people, IF I know other people to ride with. But just glomming onto a paceline of strangers deosn't appeal to me so much. But if you can ride the miles, and have fun doing it, that makes it way easier, mentally.