I haven't heard of anything newer than the two that have been in use. Aricept and Namenda. Both of those are used to stabelize the patient at the level they are at. How long they last is usually a crap shoot. It depends on the patient and how quickly they deteriorate. 50 is awfully young to be diagnosed with this those....

My grandmother has been on Aricept for 3 yrs. and Namenda for two. These drugs seem to work better when taken together. At first there was a noticeable improvement, but over the past year she has slowly regressed back to the point she was when she started taking them, although she has not gotten worse than that. So, in my experience you can hopefully look for at least 3 years of benefit. I'm not sure what difference age makes; my grandmother is 90. Maybe someone younger can see an even longer benefit.