It's even worse now that multi-process is a thing even on mobile, because it means that tabs get unloaded not just when the browser feels like it (practical quality of actual implementations might vary, but at least in theory the browser should know which tabs have been recently used, which tabs might be playing audio, etc. and so make a somewhat reasonable attempt of prioritisation which tabs should get unloaded first), but also whenever the OS randomly decides that one of your child processes (containing a random set of tabs) should die.

From following the bug tracker this definitively seems to be a problem with Firefox now – I wonder how Chrome gets around that problem, though? Do they suffer from the same problem, have they found some neat workaround, or are they cheating and being specially whitelisted by the OS?