I usually fill up the tank with fresh water, mix the salt to the correct salinity, allow it mix overnight and add rock the next day. I don't know why someone would run their tank with only saltwater for 1-4 weeks ? Why delay your cycle?
I voted "wait? put it right in" b/c the idea is to accumulate the good bacteria to breakdown ammonia and nitrates for the cycling process. If you just have water circulating with nothing on it then you are just mixing salt water. The bacteria needed is not as sensitive as fish and other livestock so it should be OK.
I may be wrong but that is my understanding of the process.
Even if the bacteria are sensitive, their growth rate is fast enough that it shouldnt really matter. If its a completely new setup with uncured rock then I dont see the point of waiting more than 1 day at the most ( just to let the salinity stabilize, in case you need to add more water or something ).