I need an opinion about my roof?

My roof is about 27 years old and to my knowledge it is not leaking. I see no water spots in the ceilings of my house. I don't know about the attic and anyone whose been up there did not mention any leaks up there. I've been in my townhome for about 13 years. My neighbor told me I should not reshingle my roof if it is not leaking. There are no shingles missing like other townhouses in my court. Should I have someone to inspect my roof? I am afraid that they would say something is wrong just to get paid.