In most cases if I don't like the cigar, age isn't going to make me like it, but it may improve some.
I always give a cigar a couple chances and also try purchasing from different sources.
There was a b&m that had their glass humidors displayed in the smoking lounge, and I grabbed a Tat out and it tasted like an ashtray.
My guess is the humidor wasn't sealed and smoke got in. I tried that same Tat from another humi and loved it.

Another example, I always buy my Oliva V by the box, and I had one box taste like a musty damp basement with a gritty consistency. I was pretty frustrated because week after week, it just didn't improve and I kept purging out and dissecting them before finishing. I gave up, put these in a tupperware, came back to them 6 months later and they improved significantly. The flavors have muted some, but that wet basement taste has become nearly untraceable and I'm happy with them. I have no idea what it was or what caused it... but time was kind.