Re: When to stop...
I more or less agree with Tess.
They say not to feed perennials after about late August, because it encourages them to make new tender growth which the frosts will kill.
Best to let them harden up to go through the winter.
My Camelias are in big tubs, and have needed watering (rain water) and feeding all summer because it has been so dry.
It is during the summer that next years buds are forming, so if they are not fed and watered sufficiently then, the buds will often drop off before they flower.
Too late to feed anymore now IMO, but early next spring, I change the top 2 - 3" of compost for nice fresh stuff - ericaceous - and mix long lasting ericaceous food pellets in then to start them off for the new year.
As for bedding, I amabout to pull my annual bedding up now because the Wallflowers I have grown have outgrown their containers and need going in the ground now.
I won't feed them before winter either.