"BETOnMACE ran for almost 3 years...but the title of Dr Cummings presentation is "...100 b.i.d. two year treatment...".  What should we read into this 2 vs 3 year difference?"

I wouldn't read anything into that. First patients enrolled started dosing Nov 11, 2015, and  enrollment continued through March 2018. Patient dosing continued through mid-April 2019 to mid-June 2019 (those sites with the most patients enrolled stopped dosing and commenced last study visits first). So there is not one constant dosing period for every patient; it probably ranges from ~13-41 months. The median time in treatment for BETonMACE was 27 months, and the MoCA was administered at baseline, annually and at end of study. So they should have baseline MoCA and 12 month MoCA on everyone, 24 month MoCA on ~50% of patients (assuming the 70 year an older subgroup follows same median dosing as total population) and probably only have 36 month MoCA on a small subset of the cognition subgroup. So the most powered data will be through 24 months. 

Sources below.

BDAZ

From Dr. Cummings AD/PD 2019 presentation (assuming average treatment duration 26 months, range 14‐36 months): "MoCA is administrated at randomization, yearly and at  termination of the trial."

https://www.resverlogix.com/upload/event/42/4388386bbd26/2019-03-29---ad-pd-2019-cummings-final.pdf

From the BETonMACE rationale and design paper: "Assessment (MoCA) test is performed in participants at least 70 years old at randomization, and again at 52 weeks, 100 weeks, and end of study."

https://www.ncbi.nlm.nih.gov/pubmed/31520897

From the AAIC 2019 poster: "Average treatment-duration is expected to be 26 months (range 12-40 months). Cognition, a pre-specified exploratory outcome, is assessed at baseline and annually in patients 70 years and older by the Montreal Cognition Assessment (MoCA)."

https://www.resverlogix.com/upload/media_element/173/b9738b92dd21/2019-07-08---aaic-poster-2019-final.pdf

From the BETonMACE update news release on Sept 16, 2019: "In addition, median time on treatment will be approximately 27 months compared to the protocol’s 18-month assumption."

https://www.resverlogix.com/investors/news?article=643