What about pitching some fresh yeasties instead to get the gravity down?
This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.
Do you care if it's cloudy? At 1.057, I'd go for it. I normally have beer done in 2 weeks at the OG. But you'd need a big pitch of yeast, ferment as close to 68 as you can, dry hop on day 9, keg on day 13 and pump up the C02. It won't be clear and it'll taste pretty green.
The reasoning behind this is that there is a lot of dead yeast stuff in that old slurry that you don't want in your beer. You want healthy young cells.
Like Joe said, you may try washing the yeast. I just started doing this and have had great results. Here's a link I used to get me going: http://billybrew.com/yeast-washing
I read the link and it mentions that washed yeast can be used a few weeks up to maybe a few months after washing. Is this a reasonable estimate? I'm going to bottling a belgian golden strong in the next week or two, and probably won't make another Belgian until next January/February. Would I be better off just getting a fresh vial after that long?