I recommend the avid golfer replace their grips every six months.

As a golf professional that has re-gripped tens of thousands of clubs and who has worked in both arid and maritime climates, I recommend the avid golfer replace their grips every six months. If budget does not allow and the player uses golf pride rubber grips or something similar then at least once a month, wash the grips with warm water and Dawn dish washing soap and then re-wipe the grips with a wet towel with clean water followed by a wipe down with a dry towel. This will get a lot of the oils from human hands off of the grips and make them a little tackier like when new. It will extend the life of the grips.