Original brush life on Ametek Lamb produced vacuum motors will vary considerably from one application to another.  For specific information concerning anticipated brush life for specific applications, contact your local distributors. Brushes can normally be changed two times before armature, and other component replacement is required. On the first brush change you can expect 70% of the original life. On the second change you should expect about 50% of the original life. After the second change, the commutator is normally worn to the point where further brush replacement is not possible.