Uh, twice the exposure at 2x the miles past factory warranty (75-50 vs. 100-50) -- things break with use, not with age per se. The $1000 jump is thus a bargain, on one hand, when compared to the base rate of over 10 cents per mile.
How many miles per year do you drive? 6 year is from delivery new? Kind of costly for just 2 years more in that case, eh?