Didn't say you should completely discharge. Just that there's a better chance of resurrecting a lead acid, whether liquid or AGM than with Lithium Ion etc."Lead–acid batteries designed for starting automotive engines are not designed for deep discharge. They have a large number of thin plates designed for maximum surface area, and therefore maximum current output, which can easily be damaged by deep discharge.
Best avoided and easily avoided, IMHO.
On the topic of chargers use sparingly. No need for constant long term connection. Connecting once in a while is ok.