28GB? Are they really that stingy that can’t can’t pull the trigger on 32gb for their top of the line card? The 3090 had 24gb, the 4090 still had 24gb, and now they add a measly 4gb more? This tells me that they are probably going to keep vram mostly the same on the lower cards as well.
It should probably last you several years with no issues. Look at the warranty on the model you are interested in, and assume that it should last you at least that long.
If it does fail, well at least it’s just your render cache.