While it is generally not a good idea to run any type of electric motor without a load for a prolonged period of time you can do it. Most racers break in their brushed motors by running them at half to three quarter voltage (2.4-3.6V) for a few minutes to even a few hours to wear down and "break in" the brushes. It won't instantly ruin them (brushed and brushless). I run my motors (brushed and brushless) open (not even a pinion!) like that to work them for a few seconds but that's about it. Oh, and people on YouTube are idiots..
Never trust YouTube comments.
You can use the same bearing oil that you use for your suspension bearings on your motor bearings. Just be carefully not to apply too much but just enough. An excessive amount will burn up and turn into a powder. This could potentially seize your motor up. I would suggest Trinity Royal Oil bearing lubricant.
Comparatively brushless motors are "maintenance free" when compared to brushed motors. Due to their mostly closed design it is very hard for dirt and debris to get inside them (also making them that much tougher to clean and lubricate). Just be sure to wipe everything down after every run (or as close to every as you can) to keep as much debris as possible out of the motor can. I've been running the same two brushless motors for two years without either one seizing up. Just care for them and be sure they're clean whenever you clean your E-Revo and you'll be good to go!
Cheers,
Kyle.