Haven't you people shot enough already!?
According to the GWCT we put down 35 million pheasants per year and the bag is 15 million. Wild birds constitute as little as 10% of this number. So be honest and accept that the majority of pheasant shoots - or at least the majority of pheasants shot - take place within an artificially created environment.
Game shooting is big business, whether we like it or not, and my guess is that if the season was extended all the fine talk on here of using the additional days to "clear up excess birds" would not be replicated elsewhere. Instead people would want to shoot consistent numbers throughout the newly extended season. After all, why pass up the opportunity for another few days? At £40 a bird there's money to be made.
So more birds would be put down. If we added two weeks here or a month there we'd eventually hear the call to extend the season again. There will still be birds left over.
An alternative? Strutt and Parker's Game Shooting & Fishing census in 2015 found that the average returns on shoots were around 44%, up from 40% the previous year, so keeping track of the bag during the season should let us vary the days if we need to shoot harder.
Leave the seasons as they are. Let the birds, the countryside, the keepers, the beaters, the dogs and yes, the guns, have a well deserved rest.
Pretty much everywhere in the British Isles is an artificially created environment. But you're right that the big commercial game shoots would merely use any extension of the season for game birds as an opportunity to maximise their profits.
I can't tell you how many of those 35,000,000 pheasants released yearly are on these big shoots, a good majority I'd think, but remember that the amount of small family run or syndicate/farm DIY shoots are far more than the corporate ones. Even if some only release a couple of hundred birds.
Arguing for an extension to the pheasant season on a stalking website though is akin to urinating into the wind in the face of Storm Henry or whatever the latest one is called. You're bound to get more arguments thrown back at you than you spout.
I think about four months is about right, especially seeing as how many don't even use all that allotted time. Although perhaps a week or two more...