I'm with you. I don't think I've seen anyone braggin' they're going out 7K to 9K before changing. Frankly, with all this discussion going on in all the Lambda forums on timing chain failures AND the fact that GM has moved to change programming of the OLM, think one would be on an engine change wish to go out beyond 3K-4K miles. Still the answer to your question would be interesting to all on these Lambda forums.
I've got a suggestion, why don't you just get a UOA from Blackstone on your next change and post up.
Those are all encouraging, no issues at 8K-9K. I ordered my Blackstone kit, so I'll try to send mine in when I get it changed. Wish I had done so last time with 10K on Valvoline dino oil. This time I got PP and I'm 4,500 into it mow with 30K on the vehicle.
Ive had 2 done- one at 6L and one at 12K on engine.... the oils had 5000 and 5500.
My intentions was to go to 0% OLM--- (just like I did on my Trailblazer 0% with 11,500)... BUT
once I started reading the Lambda forums and seeing other UOA- I decided that 50% OLM and about 5000 miles would be a good place to change oil and get UOA. (also running Valvoline Premium Conventional 5W-30).
As it turns out- the oil was OK at 5000.... but more degraded than 50% It appears.
Im at 4500 miles and im thinking of getting a UOA on the current batch- since I just passed 30K.