"Sealed" Batteries - Have we been conned?

[Crazy Dazz]

Like many people, I still have functioning lead-acid batteries that are almost a decade old. The batteries on my boat are ancient, but they keep working and because I have multiples, they keep doing the job. Just keep topping them up and charging them.

I've just disposed of a bunch of batteries, all relatively new, and all expensive models, all useless, and all supposedly "sealed".
Except they're not.

They still have vents, which means that gasses and some vapour still escapes.
What they are is non-refillable.

From what I could tell, from the translucent models, they were all low on water. I toyed with the idea of drilling holes in the top, but couldn't think of what to use as plugs.

Supposedly technology has moved beyond the need to top up batteries, and perhaps for some it has, but clearly not for these.