My first misting system was a Monsoon and it worked well for ~6 months. The problem seems to be that water from the reservoir makes it into the electronics housing via humidity. This seems to first have the effect of making the durations longer than you set but eventually the duration timer stops working altogether and the unit runs until the reservoir is empty.
Since the unit automatically starts misting when it gets power, I just stopped using the built-in timing controls and got an outlet timer that would do >1min increments. The appliance timer worked perfectly until I got rid of that whole system 2 tears later.
Swapping the 2G reservoir in the unit for a 5G (or larger) bucket reduces the need for re-filling BUT a 5G reservoir is dangerous paired with a unit that might empty all 5G into the viv. Once I switched to the appliance timer, I was able to confidently use a larger reservoir.