It will, until the extensions get short then the brush will try to twist out much earlier since not held in place by the end. You won't get life all the way until the end of your added piece, it will come out before that and depending on how tightly you held your spec making the part. Sloppy work = dies quicker. If they can't braze how well will they do that? The holder has to have a certain amount of airgap to not short the spinning rotor and usually pretty big. Tell me you can't see the cockeyed twist wear when the OEM brush does that before the end of it. Some of us did that type of mod and many many years (40?) ago. BTDT. You might get a half life there.
Time is no issue for most of these, can't see anybody driving them all day long as the only vehicle available, I did that when young and people rightly though of me as crazy then too. Even so, saying time is essential = death, how the industry gets you for 300-400% more cost, they know you gotta have it. I worked parts for many years. I NEVER attach a time element to repair, it increases the cost too much, and I repair 100% of everything I own, often repairing the broken parts again with less than $10 of cost. Methods just like that but they have to have a better outcome, that's not good enough for me.
I could be wrong though. Wouldn't be the first time.
http://www.ebay.com/itm/New-Starter...14-/281316342617?_trksid=p2352135.m2548.l4275
Even with free shipping.
Found brushes in 3 other places too but at higher prices. Mitsuba SM-13 starter.