20 oz. soap

I was making a giant soap to cut up into samples to include w/ orders when Alison saw it. She fell in love w/ that giant soap and wanted one for herself. I promised her one, but kind of hoped she'd forget all about it. I was delusional, of course. So, last night I made her a 20 oz. strawberry scented soap. How long do you suppose this soap will last? And how long after Alison gets in the shower do you think it'll take before she drops it on her foot?