The link below list the maximum age for North America's native Walnut at 250 years. IMO this is definately possible. Also consider some prolific trees may be grafted or cloned otherwise so one can in theory live many many generations and have tons of clones out there.

Not sure if your wife is a "nut" or not but beware of trading in for a different model. Like used cars we all have problems lol. ; )

Here is a link that might be useful: http://bigtree.cnre.vt.edu/TreeAge.htm

Thank you toronado3800, I'm so happy for the site very interesting, wow some trees can be very very old.

Some European walnut trees are well over 200 years old. They make for incredibly beautiful gunstocks.