Hey mate,
Just my opinion but its like anything I guess. Take learning another language for example. If you do one lesson every week or whatever then its nowhere near as beneficial as doing it everyday for 4 weeks. Same goes for the MECIR I believe. A lot of students find it hard enough to remember how to conduct ADF intercepts after 3 solid days of doing them. I can only imagine having large gaps in between lessons in the learning stage would make it even more difficult to get your head around them.
Like I said though, just my opinion.