The bottom line is that some beers benefit from extended aging and others do not. If you had a high gravity beer with lots of alcohol heat, or something that the flavors just didn't mesh in, I would say it probably would benefit from aging. Something like an IPA or Pale Ale would not. It's not really an accurate description, but I would say after a certain point, beers start to get "syrupy".
As far as continuing the habit, I do the same thing regardless of the beer. I figure not drinking one bottle isn't really a sacrifice, and if it turns out to not be good, no big loss. It is nice to have a little reminder of what you've done and what it tasted like. If it's a beer that I expect to age well, I might save more than one bottle.