Unwashed refrigerated grapes stay fresh for two to three weeks, according to Real Simple. However, once the grapes are rinsed, they last only a week. Grapes are best when kept in a resealable plastic bag toward the back of the refrigerator.
Grapes should be examined carefully in the grocery store in order to select fruit that lasts a longer period of time. The grapes should appear smooth and plump with no wilting. Green stems are preferable, with grapes that don't separate easily from the stems. Red grapes have a deep red tone, while white grapes have a light greenish hue. Bright green grapes are ripe but tend to be tart.