I don't really understand the question. I like to play in organic so, so I'll answer from that stand point.
If you are talking about foliage sprays, you can spray as long as you want. Only things I would worry about is tainting the taste if spraying to long in to flowering. Some people stop when flowers come on, so go till ~2 weeks before harvest. Also if the bud is susceptible to mold, you wouldn't really want to spray them.
I personally am doing a heavy rotation of sprays, never using the same thing 2 days in a row. I mainly spray once a day, but will do it twice if I feel the plant needs/wants it. My oldest plant atm has been flowering for about 3 weeks. From here on I'll just spray the plant with plain H2O until she gets dense, and mold worries set in. (if she does, mix pack guessing game on the strain)
Plants like the sprays in general, and they are able to take in nutrients this way too. But again my opinions are from an organic point of view. I'm clueless in regards to chem spraying.
If you are asking about a clone, I'd imagine that once roots are set, you are in the clear.
If you are asking about a seedling, spraying is not necessary, but imo not a waste of time either.
If you are worried about disturbing the new plants soil, you could always just spray the soil. It is slow, but how I start most seedlings myself. You could also add a mulch to keep H2O impact and evaporation down. I just got a bale of alfalfa & timothy hay for $12 at a local feed store. Almost the best damn $12 I spent on this so far.
I hope this helped some how.
~Fuggzy:smoking: