Fermi-type questions

Here are a few interesting Fermi-type questions I've been thinking about recently (and, in one case, on and off for about 3 years). These sorts of questions are almost always trivial if you are allowed to use Google, so if you want something interesting to think about, don't.

1. Are there more trains or stations on the underground? Almost everyone I ask this starts to answer with "there's obviously more..." and then can't decide which there's obviously more of! I think I know the answer, but I'm not entirely sure. They're certainly within an order of magnitude of each other.
   
   
2. How many pints of beer are drunk per year in the Square Mile? A friend of mine had this as an interview question, I'm still not sure what the best way of getting a reasonable estimate is, although I'm confident I could get within 1/2 orders of magnitude.
   
   
3. How many swimming pools full of water does an average person drink in their lifetime? (say, for example, that a swimming pool is 25m x 10m x 2m).
   
   
4. What is the highest number you could count to? (Assume you have to count out loud, and you have to count in English. Assume whatever you like about eating/sleeping/etc.)