They are many brands of Lead Acid batteries, like with everything they are topof the line brands and crap on other end.
You don't haveto charge LAcid right away but it iscommon knowledge Lead Acid battery WILL last shorther the longer you wait to charge it, it will not just deteriorate rapidly but slowely/
The best brand is B@B brand and most expensive one.
I own LeadAcid ebike and tried Haze brand for example - too much voltage sag, Long brand not bad.
Dartaensate,
nobody said here "immediately charge" but the longer you wait , process will start.
Read a bit for example at Battery University web site