On Fri, 05 Aug 2016 22:47:54 -0400, wrote:

It just may seem that way because it was pretty weak to start with

No. It's actually true.
It's a chemistry thing.
But I forget why.

I took chemistry so long ago, that I forget why, but the chem teacher
drilled the decomposition concept into us at the time, just as he did redox
reactions and intimate knowledge of s and p orbitals.

I'll look it up, but, I'm positive that the stronger the hypochlorite
solution, the less stable it is - but I could also be wrong.

Googling, Wikipedia mentions that household bleach has sodium hydroxide
added to make the solution more basic, which also slows down
decomposition...
" Household bleach is, in general, a solution containing 3€“8% sodium
hypochlorite and 0.01€“0.05% sodium hydroxide; the sodium hydroxide is used
to slow the decomposition of sodium hypochlorite into sodium chloride and
sodium chlorate."
https://en.wikipedia.org/wiki/Sodium_hypochlorite

Further googling finds this CDC article
https://www.cdc.gov/hicpac/Disinfect...infection.html
which says "Hypochlorite solutions in tap water at a pH 8 stored at room
temperature (23ºC) in closed, opaque plastic containers can lose up to
40%€“50% of their free available chlorine level over 1 month."

Luckily, this stops after 30 days (why, I don't know): "Sodium hypochlorite
solution does not decompose after 30 days when stored in a closed brown
bottle."

But I'll look it up further so that I can back up what I said.