Grips should be changed whenever they start feeling hard or slightly slick. Normally the driver and wedges are the first ones that show these characteristics. How long a grip lasts varies a good deal. Type of grip, how often the clubs are used, how often the grips are cleaned, weather, if clubs are kept in trunk of car, etc. all effect grip life. I’ve seen players who have to change grips every 6-8 months, others have grips last 2-3 years. Most players have no idea they need to wash their grips and how much this helps them feel better and last longer.