One of the most common failures that could lead to a tank crash is heater failure. I have been keeping tanks for 12years straight and I will NEVER have only one heater again. I have never have had issues, but I have read a lot of bad things and for thousands of dollars to be killed because I didnt want to spend an extra $100 on a second heater and controller is silly. If you are truly wanting redundancy then you need to have two heaters on two controllers. Even expensive heaters are cheaply made.
When using two heaters, always have one staged down a few degrees so it will not be needed except under transient conditions and you can identify easily when the primary has failed. I also keep a third new in the box as a backup. My 150w aqueon keeps my 150g of tank water conditioned but this is based on 75 winter and 77 summer indoor temp in Texas. I have a wifi power strip to monitor current draw and I'm able to shut off each outlet if a heater fails on, which is what you can do with an apex but for a fraction of the cost.
Lacrosse mobile alerts for 99cents/mo gives me advanced warning on high or low temps in aquarium and in my house. It also warns me if it loses connection such as internet or power outage.
To prevent seal failure, I keep my heater as pictured since it is shaped like a test tube. Never keep a heater too close to another and never place in a low flow area to prevent overheating. Too large of a heater will cycle excessively causing premature failure. An inline gfci will prevent a shorted heater from tripping all of your equipment on the circuit.