it really depends on what type of quilter you are---if you always cut from yardage- you may not have a need for scraps- if you are an appliquer you save every little piece- you never know when you might need an eye or an itty bitty bird beak.
if you are a scrap quilter- you might save every strip, square or triangle, but toss the bitty pieces.
what ever you decide is the size for you- remember--- there are lots of organizations and people who appreciate your donations!!
i keep baskets under my cutting table- one for strips (used for string quilts, wrapped clothesline projects and rug hooking) one for smaller pieces, corners, squares, what ever -- when they start really building up and i realize i need to pass some on i give them to...
the area pre-school,
boy scouts,
public school art department,
senior center,
and
members here who send out requests.
i only actually toss out strings/threads, frayed little bits. everything else is recycled/used and shared.