Be prepared for change in attitude as you get older, I was very much in the same frame of mind as you and was very happy flying Air Taxi and instructing, I then got to the point where I looked at my life and asked where I was going, at which point I did move over to airlines, I was then coming up to 30 having spent about 7 years on SEP and light twins.
I have no regrets that I did not move to the airlines before I did, having thoroughly enjoyed the flying I did, likewise I has no regrets about moving onto the airlines when I did - and I have since always kept my instructors ticket valid which I still use in my spare time.
Enjoy the flying you do, but be open minded about moving on in the future
