As i say i also use mini nucs,even ones i have made myself,but tend to now use them as a last resort,when temporarily short of two,or five frame box's.I agree with taking them out of a mini into a full size nuc is good,as soon as possible.I also believe many commercial breeders take these mated queens from a mini and then straight in the post to the customers,these young queens have not been laying long enough,not asessed properly for brood pattern,because of the size of mini nucs,and have not therfore even layed many eggs.This is not good and can lead to lots of the problems with introduction,and age of queen.So the reason i use mainly two or five frame nucs are, they get a frame of young bee's, brood,a frame of honey/pollen not much more than a mini as regards bee's,you have also taken two frames from a full hive,so this helps that hive regards new combs,foundation.The young queens have much more room with full combs to come into full lay,and remain for longer in these for better asessment of brood pattern,therfore better queens for requeening,and easier introduction.They do not have to collect pollen as you have supplied this. At the end of the season you have full size frames which can be overwintered,as five frame nucs or you can use up surplus queens and easily unite the two frame nucs into full size brood box's,to make up very strong new stocks of bee's to overwinter,some of these can be your best hives the following season. You can also keep these well treated for varroa all through the season,not so easy in minis. But as has been said it does all come down to personal preference,i have just stated my own reasons why i do it this way. I have seen young queens even in 2 frame nucs,laying many eggs in a cell ,because of lack of cells,so in minis they have no chance to lay the way they should,small laying spree,few hundred eggs,no room for more,then a long wait for more laying space,i cannot see this is of any benefit at all unless you are removing them to bigger accomadation straight away,in which case why not just cut out the middle man,the mini.