It seems like around 2/3 of the base would be reset in 10 years, if each house has an equal, random chance to be sold. I think the reality is smaller homes change hands more often and larger homes less often, meaning the chance that a larger home changes hands in a given decade could easily be less than half.

(And naturally, the longer a house is held, the longer it’s likely to be held, even without Prop 13, but Prop 13 makes it a stronger sticky force.)