Hehe... I occasionally play single penny on penny slots to get the drinks flowing. I'm usually in Vegas during slow winter off-season so we occasionally get pretty good drink service if we're one of the few that's tipping in an area.

Just to state the obvious...
You've got to use your slot card, if just to receive regular marketing promo's.
Personally, I hate pushing my luck. So, if I'm ahead a bit, I'll pack up my winnings (at least temporarily).