Per your request for an update, approx 7,000km in, ice grey interior and seats still looking in great condition.
As posted earlier in this thread, I use GTechniq L1 Leather Guard for actual protection, started applying essentially day 1 from dealer.
I re-apply every 2-3 months as directed. Prior to re-applying, I clean the seats with GTechniq Tri-Clean per bottle directions (I use this for general interior cleaning too when I am not reapplying).
So far, its been great. I have had a few of instances of very visible through to lightly visible marks on the seats and also arm rests. On all occasions marks have all been removed. Some examples of it working (whether the product or not I cannot guarantee, though I am just glad i could get it cleaned):
1) One occasion I had to stop in at a random/local tyre shop (in for a quick puncture repair), I politely pointed out the manager who took the key that I had white leather and asked they approached with caution as its hard to keep clean - they said of course. I am sure they did try and were very careful, but I had a big black oily thumb print on my drive door white leather arm rest! Sigh... well, a bit of wet wiping and cleaning with the microfiber + tri-clean, brought it right out & back to normal.
2) I collected my partner from a minor day surgery, where she had an incision on leg /under thigh, they used some yellow disinfectant on the skin, which when she got out I realised had transferred to the white leather as a yellow/orange/brownish circle! The area was covered by a dressing and she had pants on too but it must of just seeped through (I didn't realise at the time she had that stuff on her leg, or I would have laid my trusty bonus Lotus towel out which always travels with me for these circumstances

). Anyway, again, a bit of tri-clean and some soft gentle circles with microfiber brought it 100% out immediately and really easily.
Unrelated to dirt or self induced stains, some minor wear already showing on driver side seat where the seatbelt runs or perhaps i brush it when getting in/out. This is a small little nick in the leather, kind of the size of the width of the metal that a paperclip would be made of? Barely visible) and also I have a couple of small roughed up leather spots on the center console, near the cup holders , probably from my keys going in and out of cup holders, which I am trying to be more conscious of.
Probs more info there than you were looking for, but hopefully it gives some insight of the (perceived) benefit of the leather protector. These forums have been very helpful to me over the past year, so maybe it'll help someone one day.