As you've noticed, it depends on the area size. Since the sprinkler output is constant as far as gallons per minute, if you increase the area being covered by going full circle or increasing the radius you get less gallons per square foot per minute so it's going to take longer. 1/2" in 3 hours sounds normal to me for a large area.

Thanks. Makes sense.

Consider rotor sprinkler heads! As long as your irrigation pipes are large enough, you can increase the size of your nozzles to put down more water in a shorter time. Impacts don't allow much adjustment.

We upgraded and it was a big improvement!

Thanks. To clarify, I don't have an irrigation system (just a lot of hoses, 'regular' sprinklers and a 4 port valve timer).

I'm assuming you're using a 1/2" impact sprinkler. Do you have the water pressure to step up to a 3/4" one? That will substantially increase the amount of water you're putting out there.

I have 60 psi at the faucet. Is that enough for 3/4"?

Also, what if any adapters do I need to connect it? And should I also be using a 3/4" hose (rather than 5/8")?

I'm thinking that 60 psi wouldn't be enough to run that many 3/4" sprinklers. I would think you'd be limited with that many 1/2" as well. Here's what I use: https://www.amazon.com/gp/product/B00004RA9Y/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

There's a base that these can be mounted on that work well.