Longer cycles yield more gains, up to a point of deminising returns which is hit at 6-8 weeks for most pro steroids/hormones.
The only reason most run m1t for 2 weeks only, is because of it's very high liver toxisity.
M1,4add is not nearly as toxic, thus it can be run for 4, 6 or even 8 weeks(max.) And it will yield much more gains this way.
It also take some time(say a week or two) to kick in where m1t kicks in after only one day.