RE: Brushless Motor Durability
With brushless motors the only wear item is the bearings, I have a cheapy Essky 400XT on a Slow Stick, I have flown it countless hours over four years and it's like new.
Now, just like your brushed motors you can cook the windings and/or damaged the magnets by overamping.
Once you go brushless, you'll never look back[8D]
Good luck,
Pete