AF CAME 4 DAYS LATER THAN NORMAL

Cierra
So with no luck last cycle , this cycle I'll be trying the SMEP.. I've looked up the steps and was wondering how accurate is it really!? Also it says to BD every other day until you get a positive OPK, then BD again for the next 3 days straight! 
I was wondering because I know it can be tiring to BD every other day! Does it really make sense to do that? I'd rather test for positive OPK then as soon as it's positive, BD the 3 days and that's it! Like what's the point of BD every other day before you even ovulate?