shawkins
Two things.
1. If you have to ask whether you should do an instructor rating or not - don't do it.
2. Instructing should not be looked at as an hour building exercise.
If you want to help people to learn, to pass on your own experiences, to develop and refine your skills in CRM, teaching, patience and situational awareness then by all means go instructing but if you just want to build hours go somewhere else. You will just end up getting bored and frustrated and not providing the student with the skills and knowledge that they have paid for and that they deserve.