If you are using a domestic oven at work it is never going to last; it will get damaged quickly, it will rust quicker than you expect and it probably will breakdown.
The microwave is intended to save time and energy on tasks such as cooking and reheating, but they have a relatively short lifespan when compared to other common kitchen appliances, and that is assuming they are used as intended, which at work they rarely are.
The average microwave oven lasts about five years with normal use, in the home, but a lot less with heavy use and poor maintenance, which is more likely at work. At work it is not uncommon for a microwave to last less than a year.
We have seen many domestic ovens in use in staff canteens, even restaurants, and the owners are complaining that they’ve had it less than a year and it is already in need of replacing. Yes – it is intended to may be be used once a day not a hundred times a day!