Depends on how picky you are. Proper amount of Slide is important in 3C. Dirt leads to zero slide and certain shots are either impossible or very difficult.
Keep it clean and the balls clean 300 will last years on a home table. 3-6 months on a public table. Occasional application of silicone (lightly) will extend the life.
Don't do the cleaning and 300 will go bad in a month on a public table. This is usually the case.
My cloth looks and plays better than most public tables after 2 weeks and its over a year old.