After reading the comments in the Greg's thread about 'Shellac doesn't harden', I started to worry about some of my shellac flakes here.
So, last evening, I dropped a few flakes into a jar and added a teaspoonful of alcohol. A few hours later, I put a small 'puddle' on a piece of glass. This morning the shellac on the glass was clear, hard, and sanded to a powder. I was relieved to know I could still use the remainder of those flakes, if necessary.
Those shellac flakes were the last of a pound lot purchased in 1979 (I put the date on the coffee can- with plastic lid- that I stored them in). They'd been stored in a cool, dry basement area (3 different houses) since 1979- I kinda quit guitar building for a bit!
So, I don't think you necessarily have to chuck out your shellac flakes after a few months! I was taught that flakes have an indefinite shelf life, and this little test confirms that, for me, for this batch at least.
That said, I generally test every new batch of shellac I make these days. (I'm using the 'blonde' style of flakes, thus the leftover darker flakes from '79).
Cheers
John