I did some research on this and found that you are correct. However, everything I saw was not specific, meaning it would depend on the motor, environment, duty cycle, etc. In short, it's not something I would be concerned with.
The first vacuum I used in my shop lasted more than 30 years, with only an occasional filter change and an occasional piece of broken plastic. It was still working when I got rid of it, but I could not buy Cleanstream filters to fit.