I was also quite paranoid, and I don't feel bad about it now after the fact.
I didn't even have an ATO for a year or two.
After I set one up (a single-sensor reed-float type....very simple, brainless) I ran it connected to a large floor lamp that would cue me to top off the tank for a while.
After it seemed reliable, I kept the lamp, but added a reservoir and a pump. I could see every time it ran and for how long.
I ran it this way for 2-3 years before I was comfortable enough to take the floor lamp down.
My conclusion is that reed switches are VERY reliable.
Yours should be even more-so as your primary sensor is solid-state, you have a backup reed sensor AND it has a brain which contains some fail-safes.
That said, the ultimate fail-safe is to have a reservoir of the correct size. It should be small enough that if it totally empties into your system it won'y matter one bit. This is true of most "average" size reservoirs, but it does depend on available sump space as well as overall system size.
My system has been running for 10+ years (the "+" was from the prior owner....no idea how old it was) and has "dumped the bucket" a few times. That's in 10 years, with zero maintenance or cleaning, even after having a major precipitation event in the tank. If I'd have cleaned it somewhere along the way I'm sure it'd be zero failures rather than a statistical zero, but I'm still very happy with my system.
How's that for a vote of confidence plus a few ideas?
