Wow this is an old thread! LOL! I can still answer this though....
Back when I got back to Honor 2 in about a month and a half, it was far easier to progress in honor because Riot made the system progress much faster due to being introduced in the middle of the season. THIS season, it will take a lot longer to progress.
If your friend plays like 6 or more games per day, he MIGHT get his honor unlocked in a month and a half OR 2 months. Then it might take another month and a half or 2 months to get back to Honor 1. Assuming he doesn't get reported during any of those games because I think reports might hinder progression as well. I am currently Honor 4 right now and started at Honor 2 this season. So it took me a little over 4 months to progress up 2 honor levels. I play about 6-14 games a day on average so it is pretty slow. I might get reported a lot though which would slow it down. I likely trigger a lot of people when I tell them that the 50 minions crashing into our turret is more valuable than taking every single Krug. : )