One of the most significant pieces of advice I've gotten was from Paul Brook's "Alchemical Tools". He has a whole section on slowing down your presentations and filling them with feelings instead of barreling through them. He emphasizes the point by talking about how he does a presentation of Out Of This World that takes a half hour and is amazing.
In my show - it's an hour long and I do 5 routines. The opener is 2 to 2.5 minutes. The rest are pretty evenly divided with the rest of the time. 7 minutes is pretty common for my routines.
I have little trouble putting belief into my routines because most of what I do I genuinely believe in. Or, I am genuinely trying to do it. What I mean by that is that when I am doing a mind reading routine - I'm trying to read their mind for real. I guess you could say I'm a method actor?
The HP Lovecraft of Bizarre Magic