[ASCollins]

It depends entirely what you plan to do!
I personally restock my whole wardrobe everytime I go (every 4-5 years) as I love a Levi's and Converse outlet store. This is obviously a big outlay but I've barely spent money on clothes since my last visit.
In terms of unexpected expenses I try to sit down and go through my daily plan to think about souvenirs, gifts and most importantly when and where I should tip (check the giant tipping thread) to come up with a rough calculation. I take cash for tipping plus a little for OOP drinks and stuff. The rest I put on a credit card (that doesn't charge for international spending!) which allows me to monitor my spend but could also allow me to cover a larger unexpected item if needed. When we get back, all our holiday savings money goes to paying off the credit card and any of those big expenses can be paid off over the next month(s).