[L~R~G nor cal]

Depends. If you dont spill stuff, dont eat in your car, keep it clean, ect...

Basically just keep the interior like new and it will stay for quite some time. I have 33,000miles on my car, and everytime i use cg leather cleaner and conditioner the new smell comes out and stays for awhile.

To answer your question; its in your hands. It could be a months, or it could be years. Its all just up to how well you maintain you interior and to what products you use. But you are on the right track with the cg leather cleaner/conditioner. And buy the seprate ones(a clear liquid for cleaning and a tan gel for conditioning), not the all in one spray.