I really like the design of those finnex. The aquatop heaters I use are pretty similar.
I fear the bad component I've found in my failed heaters has typically been the power relay, not as big of a deal in the externally switched units like that finnex or my aquatop units but disastrous in the internally switched I've used when they have failed. Knowing this I think I may switch mostly to external controllers with solid state heaters like the inkbird units. I currently have one inkbird set up as a backup on my sump heaters but when they kick the bucket I think I'm going to let the inkbird do the heavy lifting.
Do you have secondary heater controls in place on some of your tanks? Example of mine, inkbird 2 gang ITC set to minimum trigger of 74, maximum trigger of 86, powered by the inkbird is one internal heater set to 78, and another set to 80. The inkbird always thinks it's supposed to be heating so it leaves the relay closed, and the heaters do what switched heaters do; both turn on by 2 degrees low of the called for temp, turn off one degree above the called for temp. In theory if one of the heaters stuck on it would only run up to 86, then slowly cool to 74. During the "cool down" all the heater temperature indicators would be off and I would likely notice the issue though maybe I should add a cheapo temp alert unit. I found running 2 heaters side by side in the high flow area my sump is, that setting one a couple degrees low reduced "slamming (simultaneous activation/temp surging) cycles" and kept my temperature curve smoother/slower while still having the extra wattage that's required when the room cools down too much.
Do any of you use temp alert units?