they last much longer this way
Oh yeah? You know you're pampering your fans because they aren't working properly. If they worked like they're supposed to you wouldn't have to worry about 'how long they last'. You don't need to do that with Asus, MSI, EVGA, or Zotac fans.
So, no, yours aren't working fine.
there is no reason to have at faster speed either they are fine with this % of speed, less than 50° i have as a temps so...
the point is that you can easily avoid their problems not that they have no problem...