As far as how long to get them chew - I leave sticks out and only take them away if we leave. Loki chews forever and ever. Sometimes I have to take them away in the middle of the night because I wake up to him chewing. For puppies and dogs who are not used to bully sticks I recommend giving it to them for like 1/2 hour to start, then maybe an hour a day. Puppies have more sensitive tummies so you don't want to give them whole stick until you know it won't give them diarrhea. They are mostly protein so you have to start slow. I don't have to ration them with my guys, but every dog is different.
Also, if you leave them out all the time they aren't as special. So if you use sticks to keep them occupied while you are busy, then definitely take them away so they are special when you do let them chew and they will stay busy.
We are going on a trip soon so I'll take the sticks away a couple days before the trip and give them new ones in the car. That way they aren't bored of sticks and they stay happy in the car