I quit smoking more than twenty years ago (yes, I'm that old!), and I still have problems with my lungs. It's not constant, but whenever I get an upper respiratory infection of any sort, from a mild cold to the flu, I develop a hacking cough that lasts for weeks, or sometimes months. And even when I don't have a URI, I can get extremely and unnaturally winded in certain situations where I stress my respiratory system.
I believe sincerely that I damaged my lungs with my heavy smoking, and while I have mostly recovered, the damage appears to be permanent. (I am grateful that I quit smoking when I did; I would hate to think how bad the damage would have been if I'd continued!)
I would always say that taking up smoking is a bad idea. In fact, I'd call it a downright stupid idea. It's expensive (and the money is basically being burned up), it's socially unacceptable in many situations, you become an addict and a slave to the nicotine, it's terrible for your health and the health of those around you, you stink, it does bad things to your skin and your teeth, and it's just a nasty habit in all respects.
Honestly, I can't think of any positive aspects of being a smoker (I did see some in this thread, but they seem trivial compared to the weight of the negative aspects of smoking).