FAQ

Cancelled. Four of five planned seasons were made. The fifth season was ultimately never made due to budget cuts at HBO, declining ratings, a high production cost, and a two year gap between seasons leading to consistent viewer disengagement. However, the series can be treated as complete. Due to the way the show plays with time periods and perspectives, several scenes in the first two seasons turn out to be flash-forwards to the planned fifth season, implying how the show ultimately ends if you rewatch them with the context of later seasons.

It's likely they are making new characters for new storylines. It's also possible that a host was completely destroyed during a storyline (such as burned to ash or blown up) and required a complete rebuild.

There are generations of hosts. There are some that have been present since the park opened. These old hosts are more glitchy, robotic and mechanical in nature. The current generation of hosts are made of synthetic blood and bone. More cyborgs than robots. It is likely when a host gets upgraded, they simply upload their personalities in to the new model. It's stated that these new hosts are cheaper to repair and manufacture compared to the older, robotic types.