After purchase, tomatoes last as long as a week in the refrigerator before they start to spoil. Keeping them in the crisper in the refrigerator maximizes their shelf life.
Even when tomatoes go into the refrigerator, they continue to ripen, which is why they continue to develop a softer texture as time goes by. After five or six days in the refrigerator, a tomato is usually not as firm as it was when it came home from the store, and wrinkles may appear on the surface. The texture of the inside starts turning to a mush instead of holding its structure.