I got a chuckle at the champagne bottle, nice way to celebrate your new 'pod. Unfortunately the tank sensors just aren't that accurate - they go as cheap as possible and accuracy is sacrificed as a result. I've found the battery and fresh water sensors are good but the gray and black tanks you have to guesstimate. Only the toilet empties into the black tank and you can see when it starts to fill up the pipe when you flush so that's your warning to empty it right away. Over time you'll get a sense for how long the tanks will last. We've gone an entire week by using the bath house for most daytime restroom trips when we are already out of the 'pod anyway. A full weekend of dry camping and always using the 'pod's toilet isn't a problem either. The low point for the gray tank is the shower basin. With full hookups you can leave the gray tank valve open so long showers aren't a problem (until you run out of hot water), and when dry camping we can get 4 Navy showers out of the freshwater tank - and since the fresh and gray tanks are the same size its impossible to overflow it.
If you have full hookups remember you can NOT leave the black tank valve open. You must wait until the tank is mostly full to ensure you get a good movement of water to flush out the contents. If you leave that valve open all the time the solid contents will dry out and ruin the tank. When I know my black tank is getting full I'll close my gray valve and get a couple of showers in to fill it up, because you want to dump the black tank and then dump the gray tank to flush out your sewer hose. Then re-close the black valve and leave the gray one open again.