Researchers say you must vacuum a spot 5-7 times weekly to consider it "clean" and twice as often for the high traffic areas. I try to follow that rule, especially with a cat in the house (who doesn't get brushed as often as she should) fur dander can build up....not to mention what Shannon and Ethan track in.
And don't forget to change your bag regularly. It is best to check the dirt level in the bag before each use. For best cleaning performance, it is recommended that you change your bag when it is 1/2 to 2/3 full. When accumulated, small dust particles can keep the air from circulating, which can reduce the suction in your vacuum. You may need to change your bag more frequently when vacuuming drywall dust, pet hair, other fine particles or new carpet. Some bagged units also offer a check bag indicator to make it easier for you to know when to change the bag.
We recently had our vacuum belt break. I could tell because the hose still had suction, but the main part wasn't spinning or picking up anything. Luckily it was a super-easy fix! You just unscrew the plate covering the bottom of the vacuum, take off the old belt and put on the new one. You can buy vacuum belts at almost any grocery store or home improvement store. We just happened to already have a few in a bag because Shannon is a pack rat of useful items.You kind of have to stretch the belt a little before you put it on, it goes on pretty tight. Then you just screw the plate back on and you are good to go. We used the opportunity to clean out all the hair and string that gets caught up in there and around the brush roller....something we should do more often.