Well, being mostly a cheap bass****, I've done some serious wader patching in my day.
I had a pair of Trek neoprenes when they first came out. They were so patched it was ridiculous, but I kept wearing them way past where I should have. A friend asked me why I didn't get a new pair; I said I didn't want to spend the $250+. He said, well than you need to figure in the $250+ you spent on Aquaseal to fix those

Anyway, Aquaseal will patch up most any waders (esp. neoprene, canvas, rubber- I have no experience with breathables) as long as you prep the surface and follow the directions. You can spread it over a fairly large area that is worn or cracking. Problem I have had is that once cracking sets in heavy, they are about toast. You might be able to get a little more out of them, but life is limited.
I assume you are talking about "boot-foot" waders with neoprene or other uppers.
And the cracking is limited to the boot area?
Do you store them folded- definately increases cracking. Same with storing in sun light.
Are all 3 pairs the same kind and failing in the same manner? Maybe it's the boots?
On the other hand, I don't think 2-3 seasons of waterfowl hunting is a shorter than normal time for waders to leak. I've run into wire and stobs that went through new waders on day 1.
A pair of stocking foot waders with wading boots are more comfortable to wear on long hikes- and you don't need to worry about the boots leaking. Stocking-foots are not available in as many waterfowl specific models as boot-foots, though.
For a temp fix, Aquaseal. Long-term, different waders/boots.