That varies- there are so many variables- how freshly they are cut, how they have been treated before you bought them and then where you place them. In a sunny spot in a warm room by a radiator they wont last as long as in a cool spot out of direct sunlight.

My wonderful lady always puts hers in the same spot, sometimes they last a couple of weeks sometimes as few as five days!

Welcome to GOY. Go up to Gardening Questions and trawl back to 11th April. Od156 asked about roses she had bought and got lots of good tips on how to treat them to keep them living in a vase, as long as possible .