Would it be possible to set it for 1 cycle per month, and have any units that return from combat automatically be due for maintenance? Ideally, having each slot with a status of good, due for maintenance, damaged, or destroyed would allow a tech to gradually work on routine maintenance at any point over a period of time, rather than being a sudden "once a month" occurrence that must be done immediately. Items that aren't brought back to "good" before the next cycle would stand a much increased chance of failure or reduction in condition. "Good" items would still have a slim chance of failure, so you'd have some routine replacement costs and tasks, but not a lot if you kept up with it. Falling behind would tend to snowball, where you'd either need to "mothball" units to prevent further deterioration until you could afford to fix them (particularly if you pick up a couple of salvaged 'Mechs you can't get parts for, or don't have the manpower to repair in the near future), sell them, or see them gradually fall apart.
I can definitely see having it pay to assign a low-level tech to each 'Mech, in addition to a more skillful one per lance to handle more serious issues and actual battle damage, and perhaps one mechanic per 2-4 vehicles, depending on their complexity (number of internal slots used). The cases where a low-level tech can't handle it should be relatively minimal, though, or else everything would be breaking down constantly.
