I wouldn't say it necessarily depends on age, but more the fish. When I first tried breeding, the male I put in was a "dud". He didn't blow one bubble.. never has, since I've had him. Anyways, really young bettas may not, or really old ones - though once again, bettas are all different.
My male betta lives all by himself and after I clean his tank he makes bubbles even though he is alone... It is normal when their alone I guess because I read it some where it just a sighn that they are healthy no matter how old they are....
yeah my two bettas are alone in thier bowl and they will blow bubblenests when they're happy (or in good condition i guess), they never make huge bubblenests but i do see an attempt. I just take it as asign that i must be doing something right
male bettas always seem to build up their nests right after a water change i have a few 2 1/2 month old juveniles that have started building little nests now, kinda cute