Expired domain merits

I have come to an opinion that Google resets expired domain's merits (traffic history, backlinks, its age) to zero once it realizes (by indexing again) that the domain's ownership and content have changed. Am I right on this assumption?
If so what is the period (3-6 months) before Google does so?

regards
neha

True in some cases but not all.
I know that in some cases some1 has got there hands on a expired domain name and kept the PR until the next update,but by that time they got some good backlinks so they only lost lil pr.

As for traffic there are loads of sites that snap up expired domain names just for the traffic that they divert to there other sites

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