Apr. 1 to Nov.15: high season, head for entry, head for sightseeing bus (optional)
Nov.16 to Mar. 31: low season, head for entry, head for sightseeing bus (optional)
A ticket can but not necessary to be valid for two days. The ticket clerk will ask whether you want 1 day or 2 days validity. Same price, the only difference is, they will take your photo and print it on the ticket for a 2-day route. Recommend you budget for 2 days