Two years.... with the same chain? You must at least keep it properly lubed. But... maybe... you should measure the chain just to be sure you shouldn't be replacing it.

I couldn't care less how dirty... OTHER people bicycle get. And it doesn't bother me to get my bicycles dirty ether. But the only way I know of to fully inspect my bicycle is to wash it. I wash my bicycle regularly. Most of the time my bike looks as clean as new. But then why shouldn't it.... it doesn't take but a few minutes every few days or weeks to keep it shiny clean and well maintained.

Here's a good little video that explains it all better than I ever could.