As with food, variety is a central point, so smoking only one blend means I'd be stuck with only one. I might make do with something like 965 or its match, or Granger, or C&D Stratfordshire, but I wouldn't be happy about it. My dad was a fifty-year Granger only guy, and he was content. With one blend, I'd smoke only occasionally.
Odd as it may sound, if I had to choose one, it might be something like MB Dark Twist or London Burley Blend. Neither are in my top 10 or probably in my top 20 favorites but might be what I would choose if I had to smoke it all the time. If I were to choose a favorite to smoke all day, it would likely be Fribourg & Treyer CVP.
A single blend for anytime, all around easy smoking would be Stokkebye LNF. It is not my favorite blend, but it is easy smoking, hassle free, good any time on any day.
The alternative would be to pick a single blend to smoke occasionally. One that stands on top of the heap in the #1 spot as a favorite. A blend good enough to treat as a treat. One to be savored occasionally. One that you don't want to become a pedestrian, mindless, all day smoke. In this case I'd select SG BBF, no contest.