I've been using the Corsair HX750 model for the past three years and it's been rock solid. I will definitely give Corsair my first choice in PSU for the next build.
It's a good move ... tho it will affect very few users.
1) Most PSUs get tossed long before they get anywhere near 7 years of age, after all how many peeps are using the PC they built in 2006 ? What would you do with a replacement ... would it have the necessary GFX card cables ? ... be Haswell Compatible ?
2) Old PCs are oft handed down or given away so since warranty would apply to original owner only, so again not much risk in these situations.
3) The extended warranty is basically an insurance policy, the cost of which is part of the purchase price. For the few that will remain in use by the original Owner after 7 years, it won't take much.