IDK, everything breaks eventually including oil and gas boulders. My Mitsubishi hyperheats are 7 years old and, knock on wood, the only thing that’s failed was a line set not made by Mitsubishi.

I’ve got LG and Mitsubishi mini splits that are from 2010 (now considered OLD from technical viewpoint, lol) . I’m comfy at 70F inside with temps being 0F outside in a 1979 house that isn’t insulated and sealed even close to a modern home. These aren’t even cold rated Heat Pumps and they’re doing fine at 5F and 14F below their rating respectively. Presuming the house isn’t too leaky air wise and insulated reasonably well, the only time need aux heat is when using old school (non inverter based) heat pumps (which are awful for winter and shouldn’t be sold anymore, but are and is what this article refers to), or non cold rated modern heat pumps when get up into Canada and Alaska. Then parts of Canada and Alaska will always need supplemental regardless. But for the lower 48? It’s fine.

Finally, completely missing and very important is reheat dehumidification. Add those and you’ve got a great article!

Almost all except the very best heat pumps reverse modes to the cooling cycle to heat the condenser during defrost.

Auxiliary heat during defrost is primarily used to maintain warm air for human comfort during defrost reverse mode cycles.

Time based defrost is from the seventies and is used on the lowest cost heat pumps.

Demand defrost based on logic and temperatures became common twenty years ago and is the current standard for conventional split systems.

Most minisplits reverse without any sort of auxiliary heat. Some conventional split systems are installed without aux heat.

Dual fuel heat pumps use conventional furnaces during defrost while the highest end inverter systems use hot gas bypass defrost. This method sends hot refrigerant routed in a separate circuit to the condenser while still maintaining inside refrigerant based heat. Hot gas is the most complex from a device required perspective.

The other need for heat strips wasn’t mentioned in the article is when the heat pump goes into defrost mode. Essentially the heat pump goes into cooling mode and the heat strips are turned on to avoid cold air coming from the vents during defrost. The outdoor coils can accumulate frost which diminishes capacity during heating mode. Basic defrost modes operate every 30-60-90 minutes as selected for a set period of time of 5-15 minutes. Newer boards monitor the time since last defrost and the temperature of the outdoor coils and only run the defrost cycle if needed. They also terminate the defrost based on the temperature of the outdoor coils with a tmer as a failsafe.

Strip heat conversion of electricity to heat might be 100% efficient, but doing that conversion outside the space to be heated..in outside winter temperatures then pushing heat into the house isn’t.