This is one of those polarizing topics. Many people love this, others, not so much. We are part of the latter.
We originally heard about it from a friend at our church who is a travel agent and how much fun she had with her grandson. So, we sought it out to do ourselves during our last trip.
It wasn’t long, however, before we bailed. First stop, we had to wait in line for others to do their thing. As a result, we got a view of everything ahead of time (we could see/hear everything they were doing) so when it was our turn, it wasn’t at all a surprise and we had to just re-experience what we had just seen. After one more case of this, we just didn’t feel it was worth the time it was taking.
Alternatively, the Agent P Adventure in Epcot was a blast. Everyone from DS6 to DS 17 was engaged…so much so that my wife and I got to have a little mini date in the China pavilion as they went off together to do the adventure in China.
Anyhow, back to your question about time…since we didn’t do much at all, I can’t comment on total time. But between the time it took to get our initial cards at the Fire house to waiting for and doing the ones we did, I’d say we occupied a total of about 45 minutes. Our friend from church mentioned that they enjoyed it so much that they spent about half the day devoted to just that! So, it all just depends.