If anyone needs a seat when me or jim or any of our crew is out & about - go ahead and plop down. We could be on a drink run a bathroom breaak or whatever.
I don't think people have a problem as long as when the person actually comes back the person is willing to move. Hell, that venue is hazardous in the dark - if ya find an open seat without breaking your neck I say go for it, take a load off and if the person shows up 5 15 or 30 minutes later just be ready to begin the quest again.
I certainly don't mind someone keeping my seat warm for me while I am out supporting the bartenders of America Yes, I like to sit with my friends - so that in between sets we can talk, make plans or whatever - during the band if I am not in my seat I'm either on the floor or goofing off - I'll make sure to tell my crew taht if anyone wants to sit there - no probs.