well, based on my personal point of view and experience, motor bearings have a really hard time at such high rpms... it`s a matter of time for the bearing to bit the dust at either 50 or 60k rpm; unless if it`s top notch [but then again, we are talking about a 35$ motor here- the bearings can`t be top notch]. some years ago, i had to have a motor spinning at 70k, and what i came up with, is two bearings put into each other, so each was spinning roughly at 35k. there wasn`t any other way around it; single bearings failed no matter the brand. what i am trying to say is that you can`t really expect a motor of this cost to withstand 60k rpms... yes the ratings can tell otherwise, but it`s tough to happen in real life. 50k has eventually seized bearings in one of my feigaos [8l], so even 50k is too much imo -especially with cheap motors. the rotor might take it, and the bearings might take it, but for how long is the question...
aveox is a different story allright... and my plett maxx has gone up to 58k rpm, with no side-effects... i wouldn`t do it continiously even if the motor/bearings are top notch though... experimental reasons however, deserve some credit :)
from what i see from the graphs, it seems that you are running with 4s [correct me if i am wrong]. thats about 48-52k rpms... don`t get me wrong, i am not saying that it`s your fault that the bearing on the ammo failed; i am just saying that it`s to be expected [kinda un-avoidable] with a 35$ motor.
it would probably have survived with a 3s lipo in the nmt, since the nmt is lighter than the emaxx and thus doesn`t require 4s to perform efficiently. at 3s, the rpms would be much more reasonable and safer. the same setup however, would be either underpowered [geared down] or inefficient [geared up] if used in the emaxx.
bearings failing is one reason not to choose high rpms... the other is efficiency, but that`s a long story to be discussed within a couple of lines...
i have a medusa 36-50-2200v2 and a 36-60-2000v2... you can safely gear up with the 50mm one that you have, although 3300kv shouldn`t need much gearing-up. assuming stock emaxx wheels/tires [or similar in weight and dimensions], i think you could run with the 15t without problems.
i currently run mine [36-50-2200v2] with a 22t pinion in my esavage, and i am quite happy [top speed is about 40mph, and everything runs quite cool]...
the same motor made my lgt [about 11,maybe 12lbs] on 5s lipo to pull wheelies all day [with a semi-locked 500k center diff]...
i hadn`t tried the 36-60-2000v2 till today [5s,lgt]...
and that`s all i am gonna say!