I am a high school teacher in a school lucky enough to have four 3D printers. They run at least one print, most days for more than half the school year. (probably 500 to 600 models a year). At the moment, the most reliable ones are the monoprice minis (one v1, one v2). The only downside on these printers is the load/unload process tends to break pieces off filament in the Bowden tube (a bit of a pain, but not impossible to deal with). I have only had to replace one nozzle in the last year.
Our Monoprice Select needs re-leveling more often (once a week/every 5 to 10 prints) for consistent printing. But otherwise is a workhorse. I have not had to replace any nozzles this year. Apart from the levelling, maintenance has been minimal.
All three of our Monoprice machines say they work with ABS, but we have only got consistent prints from PLA. However, for the price all three of the Monoprice machines are a good deal, but we do not expect them to last long.
We also have a MakerBot Replicator2X which is older (5-ish years) that prints ABS pretty consistently.