Bob - I would get the rating now with no delay. I got my instrument rating 15 years ago and intended to go straight for the commercial but work and family priorities pushed that aside. I finally decided to get the commercial this year. I am embarrassed how much I forgot over the years. There is some new material in the commercial written but a lot of it is overlap from private and instrument. AIr space, Nav questions, performance charts come to mind. I would strongly recommend you do the commercial written while the material is fresh in your mind.