If you keep the leather clean, 2-3 times a year should be enough. Dirty leather is more detrimental than clean leather that isn't conditioned enough. Dirt is just as abrasive to leather as it is to paint.
A damp microfiber should be enough to keep the leather clean on a regular basis. Deep clean as needed but if you wipe the leather down regularly you won't have to deep clean more than once or twice a year.