How do you handle the constant stream of ideas?

I don't know about your DHs, but mine comes up with the "next big thing" several times a week. Of course he doesn't follow through on one thing, ever. This week alone, he's had five big ones and he wants to talk about them for hours. Every one of them requires years of training or schooling,and all of them are completely unrealistic. 

I actually just got done with yet another conversation, this one about becoming an insurance agent. He's been  unemployed for several years and I get that he wants to help support, but why not pick training based on your background (which is IT). 

I love him and I want to be supportive, but how many times do I have to be a cheerleader when I know it doesn't go anywhere, ever? Not one of his ideas has he ever followed through on. 

How do you handle the constant stream of ideas?