Cheapest source for muriatic acid?

[chem geek]

My question is -- will it degrade in time -- I don't seem to use much acid at all.

Muriatic Acid (31.45% hydrochloric acid) has a multi-year shelf life so you should be fine. It also has a much lower freezing point than pure water (-50.8F or -46C) so unless you live in the Artic, you can leave it outside.