i should think twice before giving some advice when i know it will lead to spending 2 solid days explaining it to them

I agree, I too have such clients. Sometimes it is very annoying. I find them nonsupporting.

Might be due to their lack of knowledge and understanding.

erm... cause the one's I enjoy working with I go the extra mile? While the pain in the asses simply get what they pay for....

but what happens when the ones you enjoyed start to take the p i s s?

well, I have never been shy about firing clients... the ol Pareto Principle (80/20 rule)