i usually do many diferent strains at the same time and most finish close to the same time at least hopefully finish around same time. i really like to have a choice of different selections throughout the winter months until my next harvet.
sometimes i do end up with some that finish a little later than the rest, but those will go into flower a week earlier next time i grow them.
i guess the worst thing about have too many different strains, is all the different jars that need to be burped during cure. but after the cure is nice to open the cupboard and decide what i would like to smoke.