Rick O Shea
Striker
I don't think modern bats need knocking in too much. The old fellas used to roll them with a stump, to try and tighten the grain, but that is all taken care of during manufacture now.
When I was younger I used to knock bats in, and they used to last a season or 2. My latest bat has been going 3 years with a plastic face on and no knocking in.
I actually think the key to longevity is the ball you play against, and the pace of bowling. A new ball from a quick bowler is going to damage a bat. If you bat 6 in the 3rd team your bat could feasibly last 10+ years.
One of our lad's bat is nearly 20 years old - the middle still looks good as new.
The edges, on the other hand.......