score:6
I think casinos in Las Vegas are good candidates. They are open even on Christmas. I didn't find any official records but I had read once that the last time they all were closed was in 1963 (when J.F. Kennedy was killed). So, the casinos which existed then and still exist (f.e. Golden Gate) are the best candidates.
Upvote:-3
Official record? I have no idea.
A very good candidate? This newsstand in Viareggio, Tuscany. I don't remember to have ever seen it closed.