I've left Tourna big hitter silver sit in a racquet for a few weeks after a customer didn't come pick up. There was no notching in either the main or the Gosen sheep micro cross. I realize that's not that long and I don't know about playability.
Two years on a St. V Wilson PS85…I strung it with MSV Focus Hex 1.18. I ended up breaking strings on two of my K90's this past week so I ended up pulling out the 85. It still played great as if it was just strung a couple of weeks ago!