(CNN) -- He has entered the record books with his 600th round of golf this year, but retiree Richard Lewis is not finished yet.

The 64-year-old American has walked some 2,500 miles and hit over 50,000 shots after reaching the milestone at the Four Seasons Resort in the Las Colinas region of Dallas, Texas on Sunday.

The DeSoto, Dallas native has played as many as 54 holes in a day in 2010, but made do with a regulation 18 to extend his world record for the number of rounds played in a year by an amateur.

"I thought 400 was tough and 500 was a stretch, but 600 was what I had in mind all the time," he told the PGA Tour website after shooting an 86.

"It's a huge relief and sense of accomplishment. I can't remember the last time I did only 18 in a day."

Lewis' feat has been recognized by the Guinness Book of World Records, which lists him as the world's "most avid golfer."

He had already beaten the previous record of 586 rounds in a year set in Ohio in 1998, and hopes to reach 611 by New Years' Eve.

Lewis next wants to be recognized for playing 11,000 holes in a year, walking the same course 611 times in a year and playing 285 days consecutively to close out 2010.

Four Seasons' members paid for the privilege of accompanying Lewis for his landmark round, with the $8,800 raised benefiting the First Tee of Dallas program -- a charity that helps young people through golf-related initiatives.

Among them was the club's men's association president Frank Broyles, who thought it especially fitting that Lewis broke the record at the home of the Byron Nelson Championship, an annual tournament on the PGA Tour.

"To think this could have happened at any course in America and it happened here is just incredible," he said.

"Byron (Nelson) always said, 'Be good to the game and give back' and that's what we've done here today."

Lewis, the former president of an insurance company, set his sights on the record after retiring in 2009, and claims to have lost 35 pounds and dropped four trouser sizes in making it a reality.

His girlfriend Debbie Shaw has played some of 600 rounds alongside him, and spent others riding a cart as a spectator and acting as a photographer to document his achievement.

"One thing, he's certainly found out what persistence is," she said.