I'm not at all WL yet, and I know that you are asking the waist length ladies, but I did start here at LHCF at SL and I have worn my hair as short as about 4 or 5 inch back in the day.. I'm now MBL. My hair seems to grow in spurts. It jumped from SL to APL in about 3 1/2 months. APL to BSL was slow going that took about 10 months, maybe a bit more. I was graising MBL in June of '08. I have gained length since then, but I'm still MBL. So again, slow going.
I don't expect to hit WL until close to the end of this year. Also, I'm 5' 9.5" tall so my back is a bit long. This has an affect on how long it takes to reach your goal also. For me, it's looking as though it is going to take 3 yrs to go from SL to WL.
Everyone's hair grows at different rates, and can stall at different milestones. As long as you practice good haircare you will get to the length you want, and learn your hair's growth pattern along the way. You've done a great job so far, be patient and keep doing what you're doing. When your hair tells you that you need to make an adjustment, you know what to do.
Sorry for butting in, I'm backing out now.
ETA: Hey Chicoro, and Iris. I was wondering when you two would come in here and post your reggies.