I would say at least 2 but 4-5 to be thorough.
The Getty Center is very big and to fully appreciate it I would recommend 2-3 hours depending on how invested you are. Have fun!
It depends on who you go with and how interested you are in all of the works. Some visits I have spent all day, sometimes just an evening. There is always a reason to come back. So, just visit in the time you have. Consider the travel time, the size of the Getty, the walking you will do, and the weather. Use these factors to make your decision. Do NOT rush yourself. Just come back if you can.
All day if u can handle alot of walking
It depends on how interested you are about art and its history. I would plan at least 3 hours without rushing to fully enjoy the museum and its exhibits.
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