Not everyone can afford dry batteries and we have no data which will prove that its useful life will be more the lead acid batteries and if you know then kindly contribute. Information is repeated again and again, if you are an engineer and educated person then first couple of pages should be enough to draw a conclusion.
I never knew that thread would go on for such a long but later realized that every house has same problem. These are simple things which non-technical people donât know like once lead acid batteries will discharge then output voltage will drop from 230V AC to 170 Volts and since you said that you are an electrical engineer then you would know that electrical appliances such as computers will restart and mobile chargers will fail once voltage will drop below 220Volts.
Cutoff voltages for 24 Volt system is 28 Volts which is never properly adjusted from shop, charging rate depends directly on AMR-HR rating of battery and further can be fine-tuned in accordance with intensity of load shedding in your area.
Quality of Electrolyte available and used in lead acid batteries makes a big impact on life of lead acid batteries. Life its self also depends upon the charging system and its tuning.
I would suggest you to do a survey where 90% UPS system which people buy here are local UPS system which can be adjusted and are not tuned from shop. Systems which cannot be adjusted has a user manual which clearly says that all variables are adjusted and recommends a certain battery with certain AMP-HR ratings. That simply highlights that you should only buy those specific batteries otherwise the charging rate which is non-adjustable will fall out from specs for purchased battery.
Battery may it be dry or liquid has rules which governs its charging, discharging and cutoff Voltages. Even dry battery will die quickly if charging device is not properly adjusted or out of specs with respect to attached battery.
I hope, this will answer your question.