how much maintenance does a GPU rig take?
if you can remotely log in to the rigs and remotely control the power supply, how often would you need to physically go to the rig to fix something?
Once you set it up, it's not your first rig (so you have some experience) and you have a little luck, a visit twice a year should suffice. You would only clean the dust out of your cards. If you are less lucky you might have to RMA/replace some faulty hardware sooner, change the CMOS battery or change the thermal paste on some/all cards.