I don't understand the need to overanalyze the Teric battery. It will either work, or it won't. If it's low, charge it. If it might be low, charge it. If you're gonna use it to dive with, charge it. It's not rocket surgery to slap the thing on the charger for a couple hours. If you're trying to eek out the last bit of performance out of what's essentially a piece of life support equipment (seemingly more and more unfortunately), by prioritizing something like an extra flashlight or set of strobe batteries, your priorities are screwy. If your butthole puckers because you only get 87 days of standby instead of 90, I suggest you take up another hobby, like carving intricate sculptures into the eye of a sewing needle.
As for the fact that you can't swap the battery yourself, that's a hard stop for me. Nothing like spending $6000 on a liveaboard trip only to have tour battery choke on it halfway through day 3 of a week long trip. That's a thousand dollar day right there.....for want of a nail. Despite what SB would have you believe, the vast vast vast majority of people do not have a backup computer, and those that do, even less actually dive with them concurrently. Being able to swap a battery with one you can pick up in any jungle corner store without losing decompression data is probably the cheapest insurance you can get.