when I had my workshop in Karachi, I prepped batteries myself. Every single one worked strong as an ox and would crank the engine like it was a childs toy. It didnt lose charge overnight either. Customers had the same batteries for 4 to 5 or more years in Karachi - in all sorts of cars.
I charged more than a regular shop as the acid I bought had to be purchased personally - while distilled water was supplied to me for very little surcharge over its actual price.
The results were spectacular. I usually maintained the SG between 1.26 to 1.28 - checked with scales not a hydrometer.
You also need to protect the batteries from heat - so make sure you have some insulation or heatshield to protect from the brunt of heat. Also make sure your battery terminals are of excellent quality, not those screw press sheet metal trash you see in almost every other car in Pakistan.