The Meaning of Life, the Universe, and Everything.
Two things I found while playing is after you close the browser with the game running, the url for the level will be cached and reload the world, with the block changes saved, which is something nice I wasn't expecting.
The other thing I found I'm not sure is intended. After a number of hours logged in the same world, I noticed it was feeling more laggy, but still playable. Unexpectedly, the active game booted me out and reloaded to spawn me in a new world with new terrain while I was playing. It kept the block changes I made and placed it over the new terrain.
Losing the original terrain was kind of a bummer, but is it normal for the generated level to reset itself spontaneously?
Also, anyone know if you choose to manually reset the level, does it clear all the blocks changes, or does it keep them?
you might find more answers concerning old school minecraft on the java forum : )
concerning stability, im not sure how much development still goes into it so it may have some memory leaks or general long term instabilities. there might be some browser settings to toggle to imrpove stability. duno.