be knocking on a bit

One or two of them are knocking on a bit, but they're decent cricket players."

Martyn Williams may still be the most accomplished breakaway forward in these islands, but at 34, the dear old thing is knocking on a bit.

It may be unchivalrous to note it, but, at 35, Keenan is knocking on a bit for a role as studenty as this.

Besides, she's knocking on a bit...' 'I thought she'd been dead for two hundred years!' '

There's no question of children - "I'm knocking on a bit now" - and an obvious anxiety about the pram in the hall: "I'd be afraid I'd never write again."