The Foxes are five points clear at the top with 13 games left following Saturday's 3-1 win at Manchester City and the 39-year-old carpenter feels he is on the verge of a "life-changing" win.
Herbert, who placed the bet in August while on a camping holiday, has refused bookmaker William Hill's 3,200-pound cash-out offer.
"I am going to hang in there, I believe in fairytales," he said.
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The bookmaker will have to pay out more than 2 million pounds if Leicester win the title, with the biggest potential windfall of 140,775 pounds going to a customer from Guildford.
The victory over Manchester City caused Leicester's odds to win the league to be cut to 2/1, joint-favourites with third-placed Arsenal.
(Reporting by Simon Jennings in Bengaluru, editing by Ed Osmond)
