Adding supers September 5th, in Michigan

[harvey]

I am hoping it is not to late to add supers.  The goldenrod is in full bloom and so is my buckwheat.  Last week four of my seven hives was still working on drawing out and filling the second deep.  Now those four seem to have the second deep drawn and are starting to put nectar in.  I supered these hives with undrawn frames hoping to at least get them started drawing them out.  My other three hives are filling supers with nectar and one was almost full but not capped so I added a second super to that one.  Have my fingers crossed here.  Bee population seems to be pretty high in each hive although last week I didn't see a large amount of brood in any of the hives.   Figure I can leave the supers on till third week in september and the bees will then have a couple weeks left of the goldenrod and buckwheat.  What do the michigan beekeepers think of that?   Good plan or I am waiting to long?