IKEv1 and multiple SAs ?

["Mohan Parthasarathy" <mohanp@sbcglobal.net>]

IKEv2 (section 2.8) draft talks about the IKEv1 rekying heuristic where
IKEv1 implementations delete old SAs when a new SA is established for the
same traffic selector. Do these implementations delete the SA always in
these cases or only when they see a INITIAL_CONTACT notify message also ?
Are these common ?

Any information would be appreciated.

thanks
mohan