Lead-acid chemistries prefer light cycling and full recharge between those cycles. Infrequent excursions below the 50% depth of discharge norm will not cause much damage assuming a full charge is accomplished ASAP afterwards.

This article is about the intentional and chronic depletion of lead-acid banks below the 50% mark, followed by vigorous recharging.

For folks willing to trade battery longevity for some amount of increased capacity, common low-end targets for low voltage disconnect are:

• 60% DoD / 40% SoC, ~12.0 rested volts
• 75% DoD / 25% SoC, ~11.7 rested volts
• 80% DoD / 20% SoC, ~11.6 rested volts

Deep cycles generally extend the amount of time for a battery to complete Absorption.

• get power back into the battery ASAP after deep discharge; drive for alternator charging or run a generator to get bulk stage going. Solar alone might be sufficient but it might require meaningful overpaneling.
• increase Absorption time, or even set Vfloat == Vabs.
• if flooded, keep a close watch on water levels