From what I've been seeing out there, that seems like a really good deal!
If you think about it, even if when breeding het to het, you still don't know which offspring have the toffee gene and which ones don't. Whenever you're dealing with het toffees, whether those are toffinos (het toffee + het albino) or normal appearing het toffees, unless you breed them to a visual toffee, there will always be possible hets. If I was holding females back, I would rather hold back a toffino that I know had the toffee gene than a 66% het toffee female.