Well, at least it stops you going senile quite so soon. 🙂
Scientific research has demonstrated that browsing the web stimulates the parts of the brain involved in decision making and complex reasoning. In particular this helps older people stay mentally active.
Of course there are other ways (like bridge) but the internet can be fun can’t it? And can even be productive. Though it is probably good to do physically active pastimes as well as mentally active ones. Say, running, swimming, bike riding.