Do these quad motors wear down and loose performance over time or do they run great until the end and just die? I've had a quad for some time now (Ominus) and it seems be flying doggy. I'd swear it was faster when it was new. I have maintained it well and replaced a couple prop shafts and one motor. I'm wondering if the new motor is out preforming the others making it fly a bit off. Thanks for any input.