I've had 3 colonists sick with sensory mechanites for like 3 seasons and still going...
Yeah, I have two with the same thing... not keeping track, but I think also close to a year... I was wondering the same thing.
I think it depends on how often and how good your doctor is.
Mine disappeared after a few months sadly. I bought my infectet colonists pain stoppers, so they are much better with no downsides :D
<disappearsAfterTicks>
<min>1200000</min>
<max>2400000</max>
</disappearsAfterTicks>
It will last some amount of ticks between those 2 values.
Which would be 5:33-11:06 hrs:mins time spent in-game (without speeding up/pausing).
Nowhere near long enough if colonist is a masochist. Seriously, then it's just amazing