A long term market is anything where circumstances will change, fortunes will rise and fall and there are various permitations of the end result. A football season is the perfect example of this, but you could also say in-play betting is similar but over a shorted timescale.........so not really long term!
The benefit of a long term market is that you can make multiple backs and lays on different teams and possibilities with the goal being to green up. Greening up means that regardless of the result, you will profit. Going into the last couple of games of the premier league season, if you had the right bets at the right odds on Manchester City, Liverpool and Chelsea then you could be green across the board. If you simply placed bets on each of them now you wouldn't be green, because the odds and the book are set to provide the bookmakers with a profit regardless of hte result.
What you need to do is view the odds and the markets and take advantage of them as you move through the season. Taking our example of Liverpool, you can see on BetFair that they traded at wildly different prices throughout the season, from 60/1 to 2/7. Along the way all of Manchester City, Manchester Utd and Chelsea all had similar swings. Placing the right bets at the right time and you'd be locking in huge profits.
Couple of issues. You do need to time it right. One little tip is that after a result, the odds are always heightened. If a team loses, then their odds will drift far more than their actual chances of winning in the long run. Likewise if they win then the odds will come in by more than they should. The second problem is that to make it worth while you might be locking in a lot of your bankroll for an entire season. Add in using enhanced odds from other bookmakers and you might have a logistical nightmare to deal with, so it's not for the faint hearted.
Something that isn't a logistical nightmare is the mug bet. But the ease with which it is placed belies the issues that can come with it. Look at what happened in last night's Premier League game. You might have had a bet on Liverpool to beat Crystal Palace, it might even have been the final leg in your weekend accumulator, and you wouldn't have been on your own. This match would be considered a banker. Liverpool needed to win to keep up the pressure on Manchester City at the top of the league, while Palace, with their safety already confirmed, had nothing but pride on the line. Queue Liverpool romping to a three goal lead, before throwing it away and drawing three all in the end. If you'd bet on Liverpool to win, you'd be out of pocket.
This is known as a mug bet. You think only one team can win, but it's never that simple. Try matched betting instead. You might not win as much as you would with mug bets, but mug bets don't have a 100% success record, or even close to it. Matched betting can make you a profit, and that's always better than a loss.