@markone if you leave your o-ring out for a couple of hours you will see that they go back to there original shape the rubber there made out of is design to do this. and
you said every 4 months not once a year like i said? and yes to each there own but changing something that for one you may not replace with the right kind after wards
and changing cooliant well that's a given
all o-rings are not the same ah? check the material
O-ring - Wikipedia, the free encyclopedia
i use to use maybe 100000 o-ring's a year i now what you can and can not do with them ( body art )
as always jmo. just a thought do you change the seal on your oil pan every oil change no why cause it's over kill.