Those stock sealed can motors either last forever or fail pretty quick. I think yours was a dud from the get go if you were only getting 15-20 minutes at a time. I doubt you are doing anything more extreme than I am to kill it that fast.
There are sealed can motors like what you have in yours, and an "open" can. Sealed can motors are simpler and cheaper but not easily serviceable. Most usually have bushings instead of bearings and fixed brushes. There are some quality 550 motors that are this style, but most are basically throw away.
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This is an "open" can with an end bell that you can access the brushes, springs, and easily service it. In a crawler you typically want a higher turn motor since they generally produce more torque; lower turn motor for more speed.
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Just remember these little trucks are just like your big toys; more power and speed will lead to something else going out that you'll then have to beef up
.