Well that might be like me saying the principles in my van are the same as a ferrari, so it should be able to perform the same.
There are some very high end heaters with controllers, that may be as good, but they cost about the same as, or more than, a controller. And the controller also has other capabilities, if you wanted them, later. For instance I got tired of trying to match the colors on something as critical as PH so I added a module and probe, and now read PH through my controller also.
The controller controls the power to the heater. The controller uses a temperature probe to monitor, you ste a certain temp below which the power to the heater is turned on. Once the temp reaches that point the power is shut off.
I don't know why anyone would ever "max out" their heater, That would be askin for disaster. If the controller somehow failed to shut off the heater, it would still not rise past it's set point as long as it's not set to the max.
If I were going to worry about 2 heaters failing or a controller and a heater failing at the same time, I don't think I'd bother getting out of bed in the morning as I might get hit by lightening or an asteroid or something. I think the chances are pretty small.
Now if the controller failed and didn't turn the heater on, there would be no backup for that, except for the room temp, which usually keeps it from going fatally low. All stories I've heard of fatally low temps were do to extended power outages.
Here is a link to the type of controller I'm talking about:
Digital Aquatics