The Jaguar I have left for two months between charges, the Kia much longer, but used a little more, the Honda which had the battery fail early this month was needing charging every three weeks, but the problem is lead acid batteries take time to charge, it's not down to how far you travel but how long the engine is running for.
I was surprised, I had some 7 Ah VRLA batteries which were changed in an emergency when my father-in-law had unplugged his stair lift and it had gone flat half way up the stairs blocking the stairs as a result, then old ones lost for 6 months until he died and house cleared out.
The batteries would not take a charge, not unexpected, so put one in parallel with another 12 volt battery which was being charged, using a Lidi smart 3.8 amp battery charger plugged into an energy monitor and the pair of batteries sat at a 0.1 amp charge rate for around 10 days, then I saw on the energy monitor graph charge rate moved to 0.8 amp which is highest rate that charger will auto return to. And it sat there for 8 hours approx. i.e. 7 Ah of charge. Then using the now charged 7 Ah put second on of pair in parallel, this time at 0-12 Ah setting, so battery charger switched to zero output very quickly, and again after around 10 day the battery as if a switch was clicked charged up fully.
So I have now repeated this a few times, the caravan battery 75 Ah left nearly 9 months due to lock down, and again recovery was as if some one flicked a switch, after 4 days.
So with a battery which is never fully charged on a car, it will over time gradually sulphate more and more, and to bring back to full capacity we are likely looking at a week or more at a 0.1 amp charge rate, does not matter if charger can give 100 amp, the battery can't accept the charge that fast, the smart chargers vary how they work, but with the Lidi at lowest charge rate of 0.1 amp on a 90 Ah AGM battery in fullness of time voltage shown is 13.4 volt, the 75 Ah flooded caravan battery reaches 13.6 volt, the Jag battery charged in car hit just 12.9 volt, although this is likely due to way charger works, at 12.8 volt it jumps from 0.1 amp charge rate to 0.8 amp, and at 14.4 volt drops to 0.1 amp again, so it switches to 0.8 amp and a few minutes latter hits 14.4 volt so drops to 0.1 amp again, so catching it during the pulse is rare, however even though charger shows fully charged, it needs leaving on charge for a few days to fully charge.
We have noticed if left on charge for a few days, the Jag stop start works A1, but after sitting in drive for a month stop start does not work, as car computer realises the battery not fully charged. We have three cars, one for me, old Honda Jazz, one for caravan towing old Kia Sorento, and one for wife a reasonable newish Jaguar XE, during lock down they are hardly used, and it has been a case of moving smart battery charger around the batteries, which also includes two caravan and a jump start pack, a pair of mobility scooter batteries, and some old 7 Ah now used to power a radio, so the charger simply alternates between the batteries 5 days on each, then back to first, unless we have used a car then it can miss a turn. So works out at around every 2 months we charge batteries on unused cars. I would be more often but daughter tidied up for us, and one smart charger has gone missing.