While long term tracking is useful, and, since the amp hour capacity of lead acid batteries drops over time, even the Victron or other shunt based battery monitors will need recalibration over the years.
That does not make them useless. During a trip the day to day usage & replenishment is where a shunt based monitor shines. You can easily determine whether your solar has put back enough that you are comfortable using a high current device such as a microwave, toaster, etc. If you are recharging with a generator, you can see when your converter switches to absorption and save running the generator for hours just to put a few amp hours back in the batteries.
I have used both voltage measurements and shunt based monitors, and am far more comfortable dry camping with the Victron monitor. I've gone as long as 91 days without hookups, relying on solar. Without a good method of tracking the battery conditions, that would have been near impossible.
