Time Discontinuity in Westworld Between Characters

Every day, multiple storylines start throughout the park. If no one joins them, they restart the next day. This includes "dead" hosts getting cleaned up and put back into place (like Maeve, for example).

Logan explains this to William when they first arrive in Sweetwater, and various hosts are trying to lure them into various storylines. We've seen this several times, like every day when Dolores dropped an item out of her pack for a kind stranger (guest) to pick up.

When a guest joins a host on a storyline - whether it was invented by the host or created by the guest (as in the case of The Man in Black dragging various hosts along his journey) - that host is no longer available for other guests, and the storyline that they typically start may be unavailable too. For example, Dolores is no longer in Sweetwater dropping the item out of her pack for a kind guest to retrieve for her, so that storyline is unavailable. But when new guests arrive, there are still a myriad of storylines they can follow after being lured in by all the hosts in Sweetwater.

EDIT:

My answer is based on having watched all the episodes, and considering / discarding other possible explanations like all the guests arriving at once, or presuming there are multiple copies of each host.

To help support the previous answer's process of elimination in proving that there is a "system" to how narratives work or rotate with guests, the following is from the Delos tie-in website, which once one has the "access code", one can gleam files and e-mails from Delos data base, shedding light on operations and practices in the facility and the Park. The following is a flow-chart called "Storyline Builder Template" that shows how the Narrative Department, featuring the in-show Dolores-related Narrative and all of it's variations, work---including when the story/narrative can "reset". We also can presume that they only let so many guests in and out of the park at a time for this to go smoother and we also know from the TV show that guests can either walk in on already on-going story lines and/or they can trigger certain stories to start.

Also even though we can't prove that the Park(s) are on Earth, we can at least prove that the Park is a physical place on physical land, because we also know from the website that Delos facility is built into a cliff off of the Park and the following makes a physically tangible comparable.

In my memory I was conflated that hovercraft sequence when they arrive in the park with the space-hotel with 2001. And I said to J.J., “Is that park even on this planet?” The important thing for us was, when you come to the series you have no idea where you are. Disneyland is in a parking lot in Anaheim, but it’s spectacular and you forget where you are when you’re inside. -Jonathan Nolan