About a week if you keep it corked and in the fridge. If you are going to leave it out on the side, I would say about 3 days. Wine will start to deteriorate as soon as the air gets to it and I have heard that if you transfer the unused wine to a smaller bottle, this preserves it also. But yes keep in the fridge and it will last a week or so. A good test is to just taste it!... It's gone bad, when it no longer tastes good,!
