Fall is the best time to work on dandelions as they are small plants waiting for spring, I would never have tru green spray anything thing on my lawn with all the chemicals they use the enzeyms in the soil that break down the clippings will die and then you are stuck with the awful job of thatch removal.
If you already have this problem use Milorganite activated sewage sluge will put the enzymes back in the soil.
What I do not understand is the big thing aboutg dandelions they only seem to show up for a few weeks in the spring I can live with that my problem is creeping charlie never seem to get rid of it.
Also spot spraying is the best way to get rid of weeds never just spray the whole yard with weed killer it might not kill the grass but it's not good for your lawn.
Fall is the best time to get your lawn in shape for spring planting seed and feed if you wait to put seed down in the spring remember soil must warm to 70 degrees for seed to germinate.