Wine aging question (17 years?)

I made some cherry wine a couple months ago from my nieces cherry tree (produces nice tart cherries for wine and pies and stuff) and some cherry/white wine juice and various things.

I used the EC1118 or whatever it's called yeast that goes up to 18% usually, but through staggering my sugar and such I managed to push it to ~21% alcohol. Tastes like cough medicine at the moment, but I'm not really planning on trying it for another year or two at least.

I left 2/3rds of the cherries in the primary for about a week, and I've had the rest of them sitting in secondary for about 6 weeks now. I'm going to rack it today if I can find my siphoning tube.

Anyway, the point of all of this is that since it's from my nieces cherry tree and she's only 4, do you think a bottle will keep until she's 21? I've heard that for most fruit wines 8 years is the max age that you should really keep them for. I'm planning on staying with the hobby for the rest of my life, but it'd be nice to give her a super old bottle if it wouldn't taste any worse off then a 10 or 5 year old version.

cherries tend to be tannic like grapes from what I understand, and this is highly alcoholic, so I was thinking in this case the wine might keep well.

The only way to tell is try a bottle every couple of years until it peaks and starts its decline.
limiting oxygen when racking and bottling, storing in a dark, temp controlled humid environment will extend its life, but there is no sure fire way to keep wine good.
Just taste occasionally and when it starts declining, drink it rather than hold on to vinegar

I have a neighbor who has made wine for years. He made about 100 gallons this year from Foch grapes that he grows. In his wine cellar he has a 6 gallon carboy of Cherry Wine he made 12 years ago, still bulk aging.

Two concerns I have here. The first is this, did you ensure the cherry pits were removed before adding to primary? Lignified tissue like drupe pits can result in methanol production during ferment. Second, in terms of ageing you might end up with an aged product that is worse than the original. While the tannin will polymerise and become more agreeable, that's just going to make the alcohol stick out even more.

For what its worth, the very thing which got me into brewing fruit wines was tasting a Morello Cherry wine which my friends father made, and it was 15 years old! It was so good I immediately started brewing fruit wines, and I havent stopped since.