1 day is enough if you're good at scheduling your fast passes through the app, you plan your route well and you go on a day that is less busy. It's a lot of planning and work to make that happen, and I recommend 2 days if you want to relax and not be on a tight schedule.
2 would definitely be better than 1 if you don't want to feel rushed! So much to do, and if you catch a busy time, you'll struggle to get it all done.
It's purely dependant on what time of year you go, the summer is the busiest time of year so if you go during the summer the answer is no. The summer has much longer lines and more people that you have to travel through. You will also want to get the Disney Land app because it tells you all of the wait times for each ride and includes a digital map
I would think you want two nights, and then you can go back to the hotel during early afternoon for a break when the park is busiest, and come back in the evening
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