In bollywood, it is very very difficult for actress to survive. There is like endless supply of new actress. For actors, its pretty much opposite. Once you are somewhat established, you will have to give way too many flops to be completely written off.
Shahid Kapoor is a good example. He is in the industry since so long yet hasn't given many hits. However, he is still in demand.
Age is another factor. Bipasha is 35, yet looks in 20s. She is damn fit and hot but she is not leading lady anymore. Bang Bang will be her last big movie. Don't think she will receive any movies after that.
7