does it matter how long a cna program takes?

i have been looking at different programs for cna's and have finally (i think) picked out 'the one'. but i noticed that the class is shorter than a lot of of places offer. does it really matter if a program is 4 weeks vs. 8 or 12 weeks? i realize the info will be more condensed, but if the level of education truly compromised? anyone who is going to school, or already has, please let me know your thoughts. if you went to a shorter program, do you wish it had been longer? or if you went to a longer one, was it worth the extra time?
all the programs seem to have the same classes, and amount of hours, but the school i'm looking at has classes 5 days a week for 4 weeks, while some other are 3 or 4 days a week for anywhere from 5-12 weeks.
so does it really matter?