Does lens pen actually work and solve the purpose for removing dust or finger print from lens?
How about the longevity of these pens?
Yes, it does. And, surprisingly, even worn out LensPen still works to some degree. I find myself still using the old one, although I have a fresh one lying around.
Granted, pure isopropyl alcohol and microfiber cloth make for the best general cleaning, but LensPen is great for finishing. It's also hard to beat in the field.