Depends on a number of factors:
- ambient temperature
- how hard one pushes the unit/how well one balances feeds and speeds
- quantity of dust in the air (@RichCournoyer puts a sock over his and is still on his original brushes and bearings on his substantively similar Makita RT0701 last it was metioned: Makita RT070XX with an ER16 Collet Chuck? Yup