That was on the GT-R...Never had R888s on the M...I did however have them on the GT2 and got about 8k on them before the rears were done...the fronts went another 2k ish
I honestly think the R888 is really interesting. I think if you track it right off the bat then it actually increases the life of the tread depth on the tire. I could be wrong but it seems that after some solid heat cycles the tire actually loses enough grip that it almost doesn't wear the tire as bad.
On the GT2 I ran the first set off the car on the street in 3k miles...rear tires were SHOT! (no I wasn't doing crazy burnouts) The second set went to VIR as stickers, and then lasted 8k after that with two other track days but had substantially less grip on the track and street.
Bottom line I think its a weird tire...I like aspects of them, but overall don't think they are a great tire.
~Cicio