advancing

I have noticed that some perople talk about reamining in the same exercise for six weeks. My wife gives lessons in horse training and is very strict when it comes to form, so when i asked her to help me keep my form good, she made sure i did. I have only done the FL tuck in two of my work out, and my wife mad absolute certin it matched the book before she even began to time me. on 5/23/2011 i did 3x30s with the FL tuck. Should i keep doing it for six weeks? Ir can i move onto the advanced?

If it's easy for you and you're not very fatigued after then it's probably fine. Test to see if you can hold one for a full 60 seconds and if you can do that perfectly then its okay to move on to the flat tuck FL.