I have about a dozen bottles of miscellaneous wines i bottled in Jan 2021. A few bottles each of apple, pear, blueberry, raspberry that I need to drink up then. The corks are still good and still taste great. How long should you plan for these type lasting in the bottle? Is 3 years too long?
Longevity is hard to gauge, as it's affected by (at least) the fruit, ABV, tannin, acid, and sugar.
Many moons ago I had several batches of white French-American hybrids start to decline at the 3 year mark, and conversely I had a chaptalized "fun wine" kit last 7 years. The F-A hybrids were white grapes [low tannin], were low brix (17-19) [low ABV], I cold stabilized [low acid], and I didn't backsweeten [no sugar]. In hindsight, the lack of longevity was no surprise.
The "fun wine" was an Apple-Riesling kit that I chaptalized to produce 11.7% ABV, the residual sugar was 3.1%, and it had enough acid to balance the sugar. The only thing low was tannin. However, the longevity was a surprise, as these kits are far from high end and the fruit isn't necessarily high quality. Apparently I bumped it enough to extend the life span.
I suspect that wines made by the frequent posters on this forum are on the high edge of the longevity curve. As a general rule, we seem to exert more care and effort in comparison to bulk wine manufacturers, so we are more likely (as a whole) to get better longevity. In the same light, we also cannot get the high quality fruit the high end wineries get.
Clive Coates, British Master of Wine, has a Law of Maturity named after him: a wine will remain at its peak (or optimal) drinking quality for a duration of time that is equal to the time of maturation required to reach its optimal quality. My guess is that his rule applies to Vinifera reds and whites, so I take it as an approximation, not anything firm.
In your situation? I'd generally expect to get 3 to 5 years from a lighter fruit wine. Depending on the wines' qualities, 1 to 3 years to reach their best, and a roughly equal time before declining. The wines are roughly 1.5 years old? My best, sight-unseen advice is to enjoy them. Pay attention to each bottle you open, and record your impressions. Later on you can review the notes to see how the wines age. If the notes indicate the wine is holding a steady state, assume it's at its peak and plan to consume the batch before the wine's age doubles, e.g., if it peaks at 2 years, plan to drink it all by age 4.
My 2019 second run (Merlot, Malbec, Zinfandel) is starting to decline. The oak is actually getting harsher, not a lot, but I'm noticing it. I also note it's a second run wine and not intended for long aging, so I got more from it than I expected. I have 4 bottles left, so the problem will be eliminated shortly. The 2019 Zinfandel is at its peak now, and I expect it will be good for another 2 to 3 years. In contrast, the 2019 Merlot has not yet peaked -- I'm guessing it needs another year or so, then it will be good for 3 to 4 more. These are (hopefully) educated guesses on my part.