Board Thread:General Nerf discussion/@comment-38362264-20190302005336/@comment-27306930-20190304020122

You can safely use two IMRs on stock motors. It will handle three, but that's almost twice the rated voltage, so it's going to shorten the motor life.

Many Stryfe users run three IMRs until the stock motors burn out, then they replace them with decent aftermarket motors. From feedback I've gotten, they'll usually last about a year with normal use.

What really kills them is heat. So don't rev the motors for long periods of time, and they'll last a little longer.