I think that cats don't handle hairballs as well as they did when they
were younger - first of all.  Secondly, maybe he is grooming himself
more?  Thirdly, my cat is also having more hairballs these past few
weeks - maybe they are getting rid of the summer coat and making way
for winter?

I use Temptations treats for hairballs and they seem to work well at
having them pass the hairballs in the litter instead of throwing them
up.  Try them.  Don't think it is a cause for alarm and the vet will
only tell you to give him something to make the hairballs pass.