Adam,
firstly it's not a race or a numbers game.
You do it because you enjoy it.
When you stop enjoying it, then do something else.
If you're curious as to making sure you're fishing effectively on your venues, then you should see if you're catching as much as the others on YOUR venues.
Size is relative to your geographical location and your access to waters containing sizeable carp.
If the biggest fish you can aim for in your locale is 20lb, then catching upper doubles would be considered good angling.
If your lake contains 30's and 40's, then catching the same doubles would mean you need to assess your tactics.
I'm assuming you're not catching many 30's and 40's or else you wouldn't have posed the original question.
You'll find most of the contributors to this forum are very helpful (except The Monk and he's just odd and Northern) and will help or advise on most topics, except self gratification.