I always medal with a new prov, and then play the rest of the week with it, before consigning it to my practice bag. I would never consider playing with a refurb, as you don't know what you are getting. I don't loose that many balls, so I can afford to play with the best. Also, direct golf do provs at Ł28 per dozen. This seems a good deal.
That said, I must have about 100 brand new provs and Nike one platinums in cupboard at home. Probably won't need to buy a ball for a couple of years.