Well, I have had mine for 5-6 years and it is starting to fall apart. But it was a cheapo (under $100 Amazon unit). Still more than got my money's worth out of it. You can get a Harbor Freight on (~2.5 liters) for $80 which would last at least a few years until you learn the function and limitations of these things.
Most will have a built in heater. Of course the UT process itself generates heat too. Mine has never been hot enough that it would burn my hand, but it would release some steam.
I use LA's Totally Awesome in mine. I buy it at the dollar store and don't really worry about reusing it since it is literally a dollar. You can get a gallon jug for ~$4. After use, I dump the dirty Awesome, wipe it out and it is ready for next time. You could use water and some Dawn dish soap and probably do just fine too.
A toothbrush works wonders for the really grimy stuff once the UT loosens and heats it up. For the most part, you put stuff in (carb), hit the start button and it comes out clean.
There is a disadvantage to a very large one, and that is using more cleaner and / or making it deep enough to cover your part. Think about your small saucepan vs your large spaghetti pot in your kitchen. When you dump the water out of your half full small one to the larger pan, it barely covers the bottom and isn't deep enough.
Honestly, I don't know how I lived without one. Started off with a very small one designed to clean jewelry.
Ideally you could find one from an old dentist or doctors office. If you could get ahold of an old professional grade one, it would maybe outlast you.
This one would probably suit your purpose:
https://www.ebay.com/itm/Pro-160-Watts-2-5-Liters-Digital-Heated-Ultrasonic-Cleaner-Dental-Gun-Tattoo/140333938761?hash=item20ac8df849:g:fYoAAOSwtfhYqbg 4
Don't buy the little $34 one, it is too small.