its been 28 months for a local 65amp & 85amps in 2 cars. 23 months for a 120 amps AGS batteries.
I flushed both car batteries step wise after 14 months as GURU mention in other thread. Got a new Hydrometer & gave 8 bottles of aquafina water to a battery shop at garden market to prepare BATTERY KA PANI for me. Playing with acid at home was high risk.
Now I use that freshly prepared water to top up if & when necessary for all batteries.
All 3 are working great ^5