Take a gravity reading. That's the only way to tell. Mine bubbled for at least 4 days, but who knows, you're fermentation may be finished. Also I added the spices when I transferred it to a secondary. If you don't plan on a secondary, just add while kegging.
I was actually a little disappointed by the lack of spice from my hydro sample right after adding. Hopefully it will come through more. Or I can always add more since I'll be legging.
Just racked this over. Added my spice tea. I tasted it before the spice tea addition and thought the body was great and while you didn't taste the pumpkin per se, you can tell what it was. After the spice tea, (1 and a half teaspoons of pampered chef cinnamon plus) it wasn't over spiced. I...
You're going to have to constantly measure your specific gravity during fermentation to determine when to stop it. The easiest way would be to have done the recipe like normal and added some unfermentable sugar like lactose to back sweeten it.