I'm in it for the long haul with my '21 Sierra. I do my oil changes earlier than what the OLM says, usually around 25-35% life left, which usually comes out to about 8k km. And the tranny fluid I do at 50k km despite them saying it's a "lifetime" fluid. Already done it once, probably the next one will be in the spring. I'll also do the diffs then.
From a FB group on the 10 speed issues, seems to be the 3/4 ton (2500) and up's "Allison branded" trannys that have been having the most failures. My 1500 did get an extended warranty but what good is it if there are no replacement parts or whole trannys available? It's a minimum 1 month wait and dealers have a lineup waiting. There's supposed to be a third version of the valve body that's supposed to fix the problems but nobody is holding their breath.
I have to say I've been lucky with mine so far (knocking on wood!).