There is mo reason the right alloy mix shouldn’t last a lifetime, but I do prefer steel.
I get that, and I guess because I'm not a big vibrato user and block most of mine, I haven't had an issue with durability or sustain for that matter.

Interesting side note though: I had a early 70's one-piece MAZAK vibrato bridge that lot's of people considered real rubbish, and I sold it for pretty good price to a collector that wanted period-correct hardware for a restoration.