I am sometimes envious of people who have just one big website which they focus on. I can see the advantages of having just one thing to concentrate on. The problem I have is that I am always thinking of new ideas and always thinking the next site I develop is going to be “the one” that makes it big.
What I then end up with a hodge-podge of different websites. As long as I don’t have to spend much time maintaining them and they are able to grow by themselves with user generated content, I can’t seeing it being much of a problem. Adsense always seems to be up and down but every now and again I am approached by companies wanting to either advertise on my site or run an affiliate program.
If you only had the one site you will be limited by these different opportunities.