My advice at this point: Buy where you want to stay, but generally avoid the 2042 resorts.
For the 2042 resorts -- Doesn't matter whether you're happy owning for only 19 years. It's a question of what happens after 19 years.
If you spend $20,000 on a 2042 resort -- As of January 30, 2042, you have spent $20,000 + closing costs + 19 years of dues.
If you spend $20,000 on a 2064 resort (for example), as of January 30, 2042... it's a pretty safe bet (but not guaranteed) that you'll be able to re-sell for $20,000 or more. Assuming a flat $20,000.... That means you'll be out only 19 years of dues. Look at it this way, with the longer contracts, you get your purchase price refunded after 20 years!
Going back to buy where you want to stay:
If you love Riviera, it's fine buying re-sale there as long as you're comfortable exclusively staying at Riviera. You might be able to swap points with someone else on rare occasion to try something different, but you should expect to be staying exclusively at Riviera.
If you love Poly, just remember we don't know the association status of Poly2. But if you are happy with Poly studios and trading into other legacy resorts, Poly is an excellent choice.
SSR is a good value... It's a nice resort. But I don't see it as true "deluxe" as some of the other DVCs. It's not connected to a park, doesn't have great on-site dining (but Disney Springs is nearby!).