How long will the HF ultrasonic cleaner hold up to occasional use? How long will it last during daily use? Is there any brand that is even close to the price of the HF ultrasonic cleaner?
HF is a roll of the dice, some will be DOA, some work a few months, some cockroaches may eventually learn to use.
Daily use, I would buy one, make sure it works, then still get the extended warranty before the time is up to get one. If you get the extended warranty and its DOA they replace it, but you need to buy another warranty "I Think".
Other option, skip directly to a premium unit, and no it won't be anything like the HF price.
My concern with something flammable, would be the humidifier effect, you know how an ultrasonic humidifier throws off a ton of vapor, if a cleaner does something similar with a flammable liquid it could get nasty.