^Doesn't the warranty extension give you a hint of the proximity of the issue?
The reason why this extension was made was mainly because many console which have been suffering this problem had been happening outside warranty for the unmodded consoles.Hence MS had to extend it for the existing users as well as a goodwill.This is way back when the problem had first taken root & then was reported on a large scale.
You can read this 1UP report which was back in Feb 2008:
*www.1up.com/do/newsStory?cId=3166259 OR
*www.joystiq.com/2008/02/14/xbox-360-failure-rate-at-16-warranty-provider-reports/3 OR
*blogs.guardian.co.uk/games/archives/2008/01/22/the_xbox_360_failures_the_inside_story.html
Modding the console has very little or nothing to do with the console facing RRoD issue.A large portion of it is caused due to overheating of the console.Poor ventilation with prolonged hours of gameplay may lead to this incident happening on any console.Just because you haven't got a single RRoD till now doesn't mean most Xbox 360's are safe from the issue.It is persistent in all versions.Modded,unmodded,foreign,alein,elite.You name it & that has it.If you haven't got it till now, lucky you.But don't expect a full replacement of the console with it suffering an RRoD post a year.
I am not here to say anything bad about the console.But just to inform you that stating RRoD issue being more prone to modded console is a joke.The console is rock solid when it comes to features & other things but reliability is the biggest question for all of these next-generation consoles.And yes, that includes PS3 too.