Ok...so I haven't used any of my vintage vacuums in about 3 months because I got myself worried that the motor brushes will run out while im using one. What happens when the motor brushes run out?...does the vacuum make a weird noise then just quit?...I want to use my vintage vacuums again...The motor brushes on my 115 are fine... but im not to sure about my dial-a-matic, model 63,model 700, etc.