Failure rate for Cat 7155 shifters?

[Hammer]

On my second M920, I just had to replace the shifter. The one it had was 'rebuilt' when it went through depot, but it never felt right. I started to get hard to shift, and had a few other issues.
So, last weekend I swapped it for a new one from fleebay.
It shifts great, like it is supposed to! Which is a nice change of pace.
After reading a number of other posts about other people on here getting spare shifters for their 915/6/7/20 trucks, I am tempted to do the same.

My question is, how often do they actually fail though?

My first M920 had shifting issues, but that was needing to get some oil in the air lines. Cleared those up pretty quick with a little air tool oil.
Second M920 doesn't have this issue, just the shifter itself.
I have driven these a bit. Not a huge amount of miles, but I have used, driven and worked both trucks.

I don't mind the money spent on a shifter. It really isn't that much.
But is this something I really should expect to fail that often?

Btw, which source on fleebay (or otherwise!) do you recommend to buy from?

 

[NDT]

If you run the 7155 it makes sense to have a spare shifter for each truck. One day soon the supply will be exhausted and then finding one if needed will suck.

 

[Hammer]

I agree with having spare shifters. I am a 'one is none' kind of guy.
And you are definitely correct on the supply running out sooner or later.

I plan on getting at least and extra shifter, but if they fail THAT often, I might get more. If not, then I have a spare, and the one I took out to rebuild myself.