Marijuana Addiction?

Okay, my partner has FINALLY decided to quit smoking dope after i told him that if he continued i wouldnt be with him anymore. Whats to be expected of his withdrawal, he has been smoking daily for close to 8 years now.
How long will the worst of his withdrawal last and does anyone have any experience in this? Please help me out, i want to insure that he feels comfortable while he is going to feel crap! Thanks heaps!

: http://alcoholdrugstreatment.info/marijuana-addiction-3