How long can I keep VWP in fermenter?

[Steeev]

Well, I finished my first barrel of beer, and was a good boy and rinsed all the gunk out, soaked it in wasing soda for 30 minutes, gave it a good clean, and then filled it up with 5 gallons of VWP solution and left overnight.

It's payday on Friday, so it's one last hurrah before the summer arrives with it's damned hot weather. B)
I've heard that VWP lasts for a while, so I was wondering if it would be ok to just pour the VWP straight into my fermenter now with the spoon etc., and leave it there until brew night on Friday?

B*gger... Just realised that it's probably not doing the S30 valve on my barrel much good... I think I'll transfer it over now and await an answer

Cheers all.