I did go out on the Friday right or wrong, but it wasn't because I couldn't handle a weekend without getting on the turps: part of my reasoning was that you have to sit an OSB with the group at the end of the two weeks that mostly (on the Thursday) involves team exercises that would obviously be a lot easier with a close-knit group. I think blowing off some steam on friday helps in that regard.
I did feel at times as though I really did need a bit of extra study (though I would have thought that regardless!), but being the sole FSP candidate not to go out for a beer would have hurt a lot more than it helped, I think.