We had a whole load of fruit trees flower last year and despite seeing bees on them, not a single one produced any fruit. I think we had a frost just at the wrong time. So the pear trees, plum tree, prune tree and apricot tree flowers but didn't fruit, yet the apple trees all had fruit, as did other flowering bushes such as blackcurrant, redcurrant, whitecurrant, raspberries and several others like olive, fig, the grape wine and so on. Most of the trees here are +60yrs old with the exception of the olive trees (sadly). The lemon tree is a similar age as well. So I'm not sure that age has anything to do with it. The dual graft pear tree is over 60 yrs old as well and until this year has yield over 100kg of pears each year.
Hopefully next time round the weather will be in its favour again and we'll get fruit. But for this year, no fresh pears.