Is the idea to go for as long odds as possible? If so why would anyone go for lower odds?
I made a post about what odds to go for on the thread outlining technical stuff. I'll paste it here:
NEWBIE
Matched betting – back bet odds
Qualifying bet
This is the back bet you make with bookmaker and lay at the exchange, with the result that you neither win nor lose any significant amount of money, but qualify for a free bet with the bookmaker.
Qualifying loss and odds
If you take a single Event X, and compare back bet odds at a bookmaker and lay odds at an exchange, you will see that the lay odds are usually longer.
Bookmakers deliberately pitch their back odds shorter than the available lay odds. This scenario – shorter back odds and longer lay odds - means that backing Event X at the bookmaker and laying Event X at the exchange will always create a loss of money overall. Longer back odds than the lay odds creates a situation where a matched back/lay would generate cash, and bookmakers don’t like punters doing that (hence they track their back odds to always be shorter than lay odds).
So our qualifying bet will usually lose money. We don't mind losing a tiny bit of money in our qualifying bet, because the profit we make from our free bet will more than cover the loss. But we want to minimise this loss - called a qualifying loss - as much as possible.
The best way to minimise your qualifying loss is to make back bets and covering lays at odds that are as closely matched as possible. This tends to happen at short odds, where there is less wiggle room for big gaps to appear. In addition, bookmakers will often specify a minimum odds value that you must bet on with your own money in order to qualify for the subsequent free bet.
Therefore, your qualifying bet will typically be made at odds of around 1.5-2.
Free bet
This refers to the free value/voucher you use as a stake to make a second back bet with the bookmaker. When making a back bet with a free stake, we want to maximise our % profit of the free bet value.
Free bet odds
I'll write an explanation downthread, but for now, all we need to know is that the longer the free bet odds = the greater % of the free bet we make as profit.
Examples:
Odds of 3 will return a max of 66% free bet value.
Odds of 4 will return a max of 75% free bet value.
Odds of 10 will return a max of 90% free bet value.
Remember: the longer the odds you make your free bet at, the greater the value of your liability in the exchange, the higher your balance needs to be at Betfair.
Be aware: Bookmakers are very quick to see that a punter is making bets at short odds when it’s their own real cash being staked and then placing free bets on stupidly long odds. Don’t be greedy.
Therefore, your free bet will typically be placed at odds of 4-7.
Overall betting pattern
A profit making matched bet comes in two parts:
First, the qualifying bet on Event X (and associated lay), where we expect to make a small loss overall
Second, the free bet on Event Y (and associated lay), where we expect to make a profit of 75% of the value of the free bet (or more).
Therefore, in total, to finish a standard bet/free bet offer, you will be making four bets. Depending on the time it takes for your free bet to be credited, it could take a few days to complete a round. If your free bet is credited instantly, you can turn the set over very quickly.