I "piggybacked" my proposal on the end of an evening out with her friends (who flew in from out of town). I proposed (effectively) on the way out to the car for the drive home - I dont consider that piggybacking, nor have I heard any qualm from her
but I've only been married 3+ years...
On a serious note, wasnt there a thread not long ago about "questions you should ask each other before marraige" (kids, education, religion...) It was a DAMM good list and I should dig it up and link - I'm serious when I say that you need to take some evenings with your woman and go over the list - at least discuss/open up for discussion the things you guys haven't talked about already.
Go Botnst !
or maybe do this after she says "yes" =)
-John