Basically approximately an hour in the ultrasonic is the equivalent to about a week of steeping (give or take depending on a couple factors, i.e. glass transmits ultrasonic waves better than plastic).
You can get a cheap one for as low as $35 but those are way too easy to burn out the motor on unless you're very careful about how long you run it at a time. (Let it cool down after every half hour of use.)
Yes, I burned out my cheap one that I already had before I started vaping (used it for cleaning jewelry) and bought the $70 Harbor Freight model which is what I'm currently using. But it's only got an 8 minute timer, and no way to force the timer to stay on like you can with the cheapie one.
Several people on the Ultrasonic thread have recommended a couple models from eBay and Amazon. I'll look all this up again if you're interested.
PS - put your bottles in a ziplock baggie before placing in the Ultrasonic to preserve the labels.
.☆¨¯`*★。。☆ Why fit in when you were born to stand out? ― Dr. Seuss `.¸ღ¸.