I like boiling mine in vegetable stock, and serve with a nice crusty bread.
I've boiled a lot of bass strings before, and it helps a little. I've also tried cleaning them with Mennon Skin Bracer aftershave. I don't know if it really cleaned the strings, but my guitar case sure smelled great! I got that tip from Billy Sheehan.
Getting the dirt and grime out from between the strings is good. But, there is physical damage that occurs to the strings as a byproduct of playing, and no amount of boiling will fix that.
If you do boil your strings I'd just leave them in the pot for 20-30 minutes. Do not shock them with cold water afterwards. Just allow them to cool on their own, and make sure they're dry before you put them back on your bass.
Finally, you might want to use distilled water for this. I'd never thought about until now, but I can see that if your water is very hard how you could just deposit more minerals (crud) in the strings by submerging them in the hard water.
Greetings from Austin, TX
Ken