Gas is pretty binary it is either leaking or it is not. Almost never will it go from a 0 to a 1
So unless you have tenants using your gas pipes for pull-up bars you are probably in good shape.
That being said even if the do in fact use the gas pipes for pull-up bars gas STINKS. Everyone knows the smell of NG and knows to call it in right away.
So to answer, no I dont worry even a little about my gas pipes. I do have my furnaces serviced but not leak checked. That feels like an awesome scam though, go around to the rich neighborhoods offering $49 leak checks. Go down in the basement, take a big whiff "Nope, no leaks here!"