search for "perpetual harvest" and you'll find plenty of examples (such as mine...). It could be done with reliable seeds, but cloning takes a number of variables out of the problem, and is def the way to go. If you got your clone technique solid, then you should have no problem setting up a system. It's all a matter of getting the timing right - cutting clones, how long to veg so they fill the flower space (but not too much), how long to flower, etc.. figuring all that out takes time and is obviously depends on strain.