You're looking at 10 years mate on average for the Mach II, ST and *possibly* the GT, although the GT is a bit of an unknown in that department. It's certainly not going to be anything less than that.
I thought the only reason certain fridges came on and off were mainly to save power... I would imagine leaving on constantly wud do a lot less damage than turning on and off due to expansion and contraction of materials
nice1, i tend to change most of my rig every few months but ofc i cudnt afford to change phase every few months so if it lasts me a cpl of years im happy