Well, for me, once again, this business has become a game of quarters. I'm squeezing as tight as I can. If I was paying a tech, or even a hired hand to replace these brushes I would figure that into the mix. But I'm doing it. Once a year I can change all brushes at a five vacuum wash in 90 minutes with less than $40.00 in parts. Thats the cost of one motor.
Lots of opinions on lets of stuff. The only real answer will be found thru empirical research. Get a Cheap one and a more expensive one. Mark the cost and date with a Sharpie. Replace them both at the same time in Dual motor vacs and see if longevity justifies the added cost.
The same study would be interesting if done with brush replacement. (Do only one in a dual motor vac and see what happens. Of course you'll need a decent sample size) I think i saw an article recently where the mfgr indicated brush replacement would extend the lfe 50% and if done a second time by anotehr 25%.
As I indicated the factors of total time vs usage time may play a role. total time allows corrosion to occur versus usage time which is oure usage wear and tear. If usage wear occurs over along period, then brush replacement while extending usage wear will not prevent or extend corrosion issues. Climate may also play a role in corrosion issues.
My motors typicaly look so horribel when they go bad I doubt brush replacement would have done much to extend the life.
I splurged for the extra $8 on the lamb motors on Randy's reccomendation. Testing them side by side is a great idea but I'm so damn forgetful that by the time 1 wears out I won't remember what the test was! I also bought new brushes for all of the old gs motors I have already.