Meeb has hit the nail on the head. If you want to instruct as a career, the trick is to keep adding ratings- make yourself as versatile as possible. There are 2 reasons for this: one is to keep it interesting (in my last job, teaching CAP509, I did almost the whole department's spinning and aeros); the toher is to keep giving yourself higher standards to attain. It is too easy to sit back and relax- I found I needed the pressure to keep improving.
It can be very rewarding- best advice is to try and work at a school which teaches long courses- you get more satisfaction from a student who comes with nothing, stays a year and leaves with a frozen ATPL, than from a succession of Flying Scholarship students, and back to square one every ten days.
Good luck!