I volunteer as much as I can and I love it! We have a running joke (where I volunteer) that they aren't going to fire us... This may be true, but if you screw up too much you will NOT be asked to come back and help.
Usually my 'payment' for helping out is a free meal (we do a LOT of dinners to help pay for things) for me, that is enough. I stay from start to finish. We do have several people who come just before the start, stay long enough to eat, then leave. Leaving the rest of us 'die hards' to clean up the mess. We don't like it, but we need to bodies to serve the meal, so we put up with it.... very sad. We could get out of there much earlier if we had all hands to help.
It seems to be the typical 'what's in it for me' attitude.
You have to pay your own bills, so 'real' work must always come first. BUT if your going to volunteer, it should be taken seriously, or don't even bother.