>So, your theory is that Red Hat have a completely independent RHEL tree in house and they have some secret society test just those kernels for years, before they become real RHEL kernels.
That's EXACTLY what happens. RHEL kernel is branched off about a year before the first beta and 1.5 years before the final release. With lots of backports, of course.
Case in point: RHEL 6 which was released on 2010-11-10 is based on 2.6.32 which was released on 2009-12-03 (and that's unusually quick turnaround for RHEL).
And they're supporting it until 2018 (at least), with backports of new features and bugfixes.
>I think you are mistaken. They would not have enough man power or wide enough configurations available for that. Their "super stable" RHEL kernels would suck big time if they did that.
They employ a lot of kernel developers precisely for that very purpose.
And that's the reason why RedHat is a big company.