some people can not stay motivated and focused enough for a long cycle, some cant continue to gain after 6-? weeks, some run dosages that should not be run for more then 4 weeks, some love orals, etc etc
some people prefer long slow steady gains, some are trt, some love long esters and a build up, some are only focused 75% and need a long cycle, etc etc
you gotta find out what works for you
for most
orals 4-6 weeks
injects 6-12 weeks
4-6 week pct
bridge 4-8 weeks
train natural 4 months
rinse repeat
adjust to for your needs