liveoffroad

I've got a G52 with who knows how many miles behind my 7mge. i've been running it for about 3 years and i'm starting to wonder when its going to kick the bucket. i've got a forward shift w56 sitting in my garage for when it does go, but i'm trying to be pro-active so i'm not swapping it out on a roadside somewhere. are there any signs that these things are on the edge of going out? i'm not hearing any bearing noise and it shifts ok for how old it is. I'd normally be a "just swap it and forget it" type of guy, but the w56 is also used so there's no telling what its lifespan will be either