Thanks for the replies guys, interesting comments I have taken onboard.
String gauge was never an issue as I have always used 10-47's on my 12string and 12-54's on my 6string and I'm still happy at that.
I have decided though, that after listening to both my twelve and six stringers re-strung with regular Martin uncoated, I shall be going down that route for sure, both instruments seem to ring, fresh & bright; and as was the point of the post, I probably won't notice any shorter string life, as the coated variety needed changing quite regularly due to fret wear anyway.
I shall now go and book that round the world cruise for myself and my wife, paid for by all the money I'm going to save by using regular rather than coated guitar strings!!!