as marc mentioned never let them see you sweat.
(TOT) time out timer, my machines are set to 3min
split PL's and never make them public.
a machine you can remotely control over the air, second input or LAN/wire line.
there are other alternatives like LTR controllers but that limits who can use the machine.
on that note I've had my share of people who jam/have no respect for the time effort and $$$$ that goes into running a machine.