Might I be better off using a TIP122 Darlington than a FQP30N06L MOSFET?
The parts you used are robust when used properly. I suspect you did not give them enough gate voltage to turn them on fully and that caused their failure. There may also have been transients on the 50V supply that caused the parts to avalanche. They are not guaranteed to be reliable with only 5V drive- you need a 'logic level' MOSFET, and I would not use a 60V MOSFET on even a regulated 50V supply with inductive loads floating about. 

When properly rated and properly driven the MOSFETs will run extremely cool and should last indefinitely. Large power MOSFETs have a large gate charge so casual ESD events actually are not normally an issue. You just have to make sure they're either FULLY ON or FULLY OFF or you'll get excessive internal heating and perhaps violate the safe operating area (SOA) specifications. And make sure they don't see excessive voltage when off from drain to source. That means enough gate voltage supplied fast enough turn turn on and the opposite to turn off. So a pull-down resistor (in parallel with maybe a 12V zener for gate voltage protection) will prevent some problems, but you must use a MOSFET specified for 5V drive if that's what you are using. 

You might consider something more like an Infineon IPP50N10S3L-16, which is rated at 100V (5x more margin than the thin 10V you have with a 60V MOSFET) and has 21m\$\Omega\$ max Rds(on) with 4.5V drive. There are other choices- you can do a parametric search. 

Unlike BJTs, there extra voltage rating costs Rds(on) vs. silicon area and also makes logic level more difficult, so the voltage rating should be enough to be reliable against transients etc. but not too much, if that makes sense to you.