Ouch!
I would sure like to hear from others how long they have gone before doing this. I am normally very conservative and dont like to push things, but my gear box has not given me any concerns yet.
Hey. I know this post is a few months old but thought I'd send you my 2 cents. I have Chassis 42 with now about 6400 miles on her. I had much the same questions and you.
I'm not a mechanic but I do all my own work on the car. So take my advice with that in mind.
My feeling is:
Yes it needs to be inspected. No it doesn't need to be pulled off the car every 1000 miles and send to Sadev.
My home track is Sebring - the most brutal track on cars because of the bumps - and I run there 90% of the time. DE, not much racing. I change the transmission oil after every weekend.
I didn't check my transmission for the first 5000 miles. In retrospect that was risky. I ended up replacing 3rd gear at that point and just replaced 1st and 2nd last weekend at about 6400 miles.
My personal schedule is to inspect every 1000 miles now. Breaking off a tooth one of the gears will destroy the gearbox.... $600 to replace the bad gear early is much cheaper than 14k+ for a new box.
Inspecting the gears is actually an easy job if you're patient and ok doing your own maintenance (or you really trust your local shop). You need 2 special tools you can buy from Sadev but nothing crazy. Basically you take the wing assembly off the transmission and unbolt the end cap from the transmission and then slide all the gear ratios and dogs out to inspect. If they are pitted they need to be replaced in pairs (primary and secondary shafts together) but only the bad gear, not the whole stack. Lower gears take the most abuse in my experience.
I use a video bore scope to inspect the ring and pinion in the middle of the case that isn't visible from the back and is a bigger job to get access to. It still looks great to me without pitting.
I plan to pull the transmission and send to Sadev for a full inspection and seal replacement this summer.
I hope this helps. I think I have a video around on how to do the tear down if that would be helpful. Feel free to reach out if you have a question.