My first conclusion when I contemplated the poster's initial question...
Nitro may seem less reliable when compared to electric, but I wonder if some of it is just perception.
Unless you have several hundred dollars in just batteries, and some good charging capabilities, you have to stop for an extended period of time after each battery pack...and even if you had multiple batteries, you have to let the elec. components cool a bit between runs.
So to compare them....elec. run a battery(6-8 minutes) - nitro run a tank of fuel(7-10 minutes)...
Elec. cool and replace battery - nitro pitted, restarted, and run another tank...
Elec. and nitro go for another run together...
Elec. needs to recharge battery - nitro runs another quart of fuel.....

Plus, I think that nitro trucks get run a bit harder generally. When it can scream like a banshee, you are more likely to send it into battle. People with electrics tend to drive more on prepared track surfaces, and treat their machines with a bit more TLC, where people with nitro trucks tend to rip up the back yard/front yard/neighbors yard, the local park, a construction site on Sunday when nobody is there...

In the end, most of the parts on either type of machine are consumables. Nothing is made to last forever. Nitro isn't inherently un-reliable, but there are a few more variables to contend with.

I know that's a bunch of generalizations, and assumptions, lightly sprinkled with opinion...but that's my thoughts on it.