when to pitch a starter (I know)

I just want to clear things up for myself here. I have read conflicting info on when to pitch a starter. I made up a starter yesterday consisting of 2.5 quarts of water, 8 oz Dme and a wyeast 1214 activator.

I added the yeast yesterday at 2pm and have been shaking every half hour or so. I was just going to wait a couple more hours, and put it in the fridge for a couple hours to decant, and let it warm back to room temp while I am brewing. But now i see that after i shake it, within about 15 minutes i get a half inch yeast layer at the bottom, which would indicate that the yeast have finished using the available sugars if i understand correctly.

So, should I let it go a bit longer, or pop it in the fridge right now because the yeast are done with their work?

I would put it in the fridge now so you can decant off the spent wort. If you're getting a layer of yeast on the bottom, you have plenty to pitch.

thanks, i appreciate it

any time frame for how long in the fridge it should take?