I recently reviewed a Philips product in response to an email, which encouraged me by offering 25% off ANYTHING ordered from their online shop! The review had to be completed by 30 July, with the discount 'voucher' being emailed before 13 August.
When the email arrived the code they gave me was Philips2012 & lasts until 9 September. I can't honestly see there being a problem with anyone using the code, it's pretty generic! I've already used it myself.