These motors are very well built. There'* no doubts there. Series 2 are also built well and can go just as long. The S1'* IMO had some things that made them last well and it'* not a bad thing, but a few items that help make a motor durable are sand bagging on the factory'* part.
S1'* aren't known to flow well, make a ton of power etc. They run well, they run forever and beating on them doesn't typically effect them adversly because they can't give much more than they do each day. That middle of the line space of good power with plenty of restrictions etc keep it solid for a long time.
I cammed my motor at 186K miles.
00 Regal GS: All kinds of cool stuff.