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You need to top-off with few ml of distilled water to keep the cells wet. Dry cells kill batteries.
Batteries will not discharge unless your bike is going on very frequent and short rides or it is not getting enough voltage from the bike to stay charged. Also a battery will only last a few years before its no longer useful.
Your several things may be causing a parasitic drain from your battery. If they are drawing more than a few mA at-rest, I think that's your problem. Use a meter and check.