There are people on other boards that have 150,000 and more on their CVTs.
However it is true that Nissan ahs not had all that much luck with them.
Even tho your Dads tranny is 10 yrs old since it only has 85,000 miles so i it should have lasted longer.
I once owned an '09 and drove it hard , loved it too..but I bought and sold it w/ lower miles.
Some put in tranny coolers and are extra religious about fluid changes and this anecdotally seems to help.
Getting a re-manufactured one from Nissan may be too expensive.You are talking 5k minimum from what I hear.
I would look to pick up a low miles used one from a junkyard.
PS: And welcome to the board.. We are primarily a Pathfinder board but within our expertise are happy to help anyone.