Comment by efuquen

Transfers take a very relevant amount of time, even during rush hour when the trains are running frequently. Aside from waiting on the train, which does not keep a strict schedule and can get delayed for many reasons there is the walking time to the other train, which can be a decent amount even in locations where you don't have to exit the subway to transfer. Factoring a minimum 5-10 minutes extra time per transfer is a safe bet.