I've lost 20ish pounds since July. BUT 12 of those were this past month on SBD. If you stick with it and exercise regularly, and don't go off plan at all, you will do your best. I don't expect to lose 12 pounds every month, though. It really just depends on you - your metabolism, how much exercise and water you get, and how closely you stick to the plan. I used to have 'reward meals' every 5 pounds. I never seemed to get very far! I am not doing that anymore. I just want to go straight through and focus.
Somebody posted here a while back 'Keep your eye on the prize' and I keep remembering that. I don't know how long it will take me. Looking forward, though, definitely seems to be a longer road than looking behind me. I guess what I am trying to say is don't worry about how long it takes you if it discourages you.
The thing is - you will always have to watch your eating habits or else gain it back. Don't look at a diet as a temporary solution. Once you get the weight off, you have to keep it off. If you go back to your eating habits pre-SBD, or pre-any other diet, you will go right back to where you started. It might take you 8-12 months to LOSE the weight, but after that, it only slightly changes to maintain it. This is a lifetime project, but your eating habits will be so much better at the end, you won't WANT to go back to your old eating pattern.
Don't give up, and stay focused! It isn't such a long ride as it looks. You'll be losing weight and feeling better all along the way, and that will probably be enough to keep you satisfied until you get there.