I used an SIP Weldmate 140 arc welder for years and always switched it off whilst positioning parts which extended it's cycle time before it shut down due to overheating; I'm like Matchless and always switch off anything when not in use which is a good safety rule. Out of interest many years ago I wound a 75KG transformer to supply my 415V three phase and it idled at only 0.8A;
This huge 75KG transformer I wound idled at 0.8A so a much smaller transformer won't bankrupt anyone if left switched on; I switch everything off for safety when unused.
I leave it on, but since I lost half a bottle of gas overnight due to a tiny nick in the connection, I always turn gas off if I not going to weld for more than 5 minutes or so.
I turn the gas off (both the bottle and the regulator), lost a fair amount once on the tig. But I noticed that the mig setup is very solid, the high pressure side didn't move overnight, neither did the low pressure side, figured that one would've leaked out really.