That's impossible to predict. I was hired onto the brasilia when I lived in an RJ domicile. People were telling me to just take it because I'd get my transition in 8-10 months and never sit reserve. The class that was hired 1 month before me never sat reserve at all. I was on reserve for a year, and the class one month junior to me never got off reserve for the whole 1.5 years it took to transition (not 8-10 months). Had I taken a jet class instead of a Brasilia class I would have lived in base the whole time and sat reserve less.

I don't think there's any period of time where you can predict how long you'll sit reserve since I was being told less than 1 month before my class date that I would never sit reserve.