I use my 24V SLA Merida ebike for errands many times during summer .
I stay in grocery shop no longer than 1/2 hour.
I think slightly discharged SLA left for 1/2 hour should not do any damage.
Often I leave it turned on when I am with my wife on other ebike so electronics/controller/ draws some current which slows down sulfur deposit of course.
What is really issue here is the quality of SLA, lot`s of Chinese crap here.
The best is B&B brand hands down, they use virgin lead and manufacture they own Pb plates not like others.
They are slightly more expensive but superior to others, I checked oter brands on my Merida, like crappy Haze brand.
Curious, did anybody saw ebike kit sold with B&B batteries, I bet NOT!!
MC