Me: My SPG is leaking, do you guy's have a spare SPG HP spool or "O" rings?
Liveboard DM: No!
Me: OK, can I rent one of your rental regs and swap the spg onto my reg?
LB DM: No, our insurance company won't allow that!
Me: OK, don't worry about it I'll just dive the way it is and only lose a bit of air anyway.
LB DM: No, you can't dive with faulty equipment, you have to rent one of ours!
Worst liveboard trip I have ever been on and the rental reg was utter crap to breath from- probably hadn't been rinsed in months. Now I always take a spare first/second and O rings.