If you don't teach these, I guess not very often :
I tend to do these only when getting checked out in a new airplane, when doing a check ride, or when doing a biannual. This gives an average of about once every 6-9 months for me.
- Engine Out (i.e. PFL or Feathering one)
- Stall recovery in cruise
- Stall recovery from a simulated approach
- Fire
- EFATO
+ Departure Stall
+ VMC demo
+ Vacuum Pump Failure (i.e. a partial panel)
+ GPS failure