I keep my tenants about 6 years on average. I keep the house empty between tenants for about 2 months so that I can do major upgrades.
The last time I turned over a house without a break I had a cleaning crew come in because the old tenants moved out at 10pm and the new tenants moved in the next morning at 9am. The over night crew cost me about $300. We cleaned and painted (touch-ups) all in about 6 hours. Since I keep updating the places, and I do repairs when they happen..I don't have much repair between tenants as such.