The reason you should disconnect your lipo, is that many ESCs that have capacitors also have a discharge resistor to discharge the capacitors when not in use. So what happens is the battery charges the capacitor, the little resistor puts a small load on it to drain it and the battery maintains the capacitor charge. During the course of using it during a day, it's so small you'd never notice. But if left it for days or weeks, that small load will eventual drain your lipo.

Not all ESCs have this setup, so your results may be different.

Lipos are super slow self dischargers. Meaning they will maintain a charge for months. I have lipos I don't use anymore, but every couple of years I check to see if they are still OK, and they are still very close to the storage voltage I left them at.