Saw this post, it's not this easy is it?
Say you start trading tomorrow. You make £10,000 in the first month. Great. Now you go and find a short priced favourite that you are fairly certain will win. Lay it for £5000 on Betfair and back it for £5000 on Daq (you are up £10k so you can do this). If it loses, you are up £15k on Betfair sure but if it wins as expected, you are now still £10,000 up but only £5000 up on Betfair. I have been doing this ever since the Premium Charge came in and have never paid it. By arbing with bookies and the Daq my Betfair P&L is fairly close to zero, they think I don't make any money. Combined with having two accounts, in different names, one at work and one at home so the IP's never get linked, I am assured of never having to pay a charge unless all of the bookies ban me or Betdaq and WBX cease to exist.
So whilst you are not missing anything, you see that this has nothing to do with juggling a winning trade while it is in play, there is no rush to offset.
But don't wait until you are £230k in front before you start reducing your "apparent" Betfair winnings.