I think your old cracked beads have great character, even if they are plastic of some sort. It seems to me, the more complex a bead, the worse it looks as it wears, but simple beads of any material - stone, glass, copal, plastic - gain character as they show the cracking, chipping, crazing, and discoloring testifying to their long use. I'd rather have old cracked plastic beads like yours than shiny new copal.