And note that the nomial 7Ah is for a new battery at a particular temperature. As batteries age the capacity will reduce, and if abused the capacity will drop dramatically. As you only want 0.5Ah per day, regular charging
should mean a long battery life.
Abuse to avoid is over-discharge (permanently wrecks the battery), or over-charging (heats up and evaporates
the electrolyte.
Normally for a lead-acid battery you'd be hoping to see the phrase "deep-cycle" or "leisure" in the description so that
you are not being sold a vehicle battery. Vehicle batteries are designed for high peak current and being
kept fully charged at all times, not long life in a deep-discharge/recharge pattern.