A problem with an NV is, I guess, that rather than get a multi-vintage blend you could get, say, an unattributed 2003. It's been my experience, though, that though I have sometimes seen some variation from one time and the next, most house's non-vintage brews are fairly consistent, at least stylistically. I was musing on this the other day when considering a Steve Tanzer 90 pt review on one of them, in fact might have been this Heidsieck, wondering how any reviewer could assign points to a non-vintage wine that means anything since the review has virtually no expiration date and may not apply to future versions.
My wine shopping and I have never had a problem. Just a perpetual race between the bankruptcy court and Hell.--Rogov