Cirrus Airframe Life Limits

I read a few posts referring to the FAA certificated life limit of the
cirrus airframes and couldn't believe my eyes. So, i did some
searching and here's what I found:

SR20 (approved 10/23/98) - airframe life limit 12,000 hours
SR22 (approved 11/30/00) - airframe life limit 4,350 hours

It's right on airweb.faa.gov in black and white.

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/91b98f5d9cf615c586256e54006329e9/$FILE/A00009CH.pdf

What bothers me is that in all the articles I've read about this
plane, it's avionics, advancements in technology, blah blah blah, not
ONCE have I read about these life limits.

So my question is - why such a huge difference between the two models?
And, does this mean the SR22, in particular, is going to be a tough
resel after someone puts a thousand or two hours on it?

Has Cirrus ever been asked about these limitations in public, and if
so what was their response?