@BFRedrocks hitting the piezo switch will cycle the settings but you have to hold it to turn it off. I think the covers are usually to prevent accidental turn-on as getting a piezo to active isn't just a "light tap" you do actually have to press it.
in terms of how long it lasts, that's impossible to answer.
The BZ400 pulls a max of 110w, the vest pulls 55w, and the gloves pull 36w.
Now, you can say that oh if you have the BZ400 and gloves, that is 146wh, so the 107wh battery will only be good for 45mins. That is true, but the vests get up about 110F when they're on high. That is HOT. Not enough to burn you, but more than enough to make you uncomfortable in all but the coldest water. These vests are designed to go with other layers of undergarments and work in addition to other undergarments instead of replacing them altogether, but still need to be over your base layer. You may put it on high to take an initial chill off, or depending on the battery may need to as the battery winds down *i.e. light monkey, halcyon, santi batteries that actually run at a lower battery voltage than the vests can take, but with the UWLD high is the same high at the end of the dive as it is in the beginning. With the other solutions, they start at 12.6v when fully charged and the vest panels are designed for 12.5-13v as given out by motorcycle alternators *the original application of these things*. When the batteries are at "nominal" voltage, it will be 11.1v and the heat output is drastically reduced. The pitkin controller for example will spit out 100% of battery voltage, but as that drops off, so does your heat. With the UWLD "nominal" voltage is 18v, so it is always bucking the voltage down to full heat regardless of battery charge.