If the season has already started and the crew is understaffed, they might ask if you want to start work that day, but there's no pressure and you don't have to. You can process in the day before, or, if the season hasn't started, a couple of days before they usually don't mind, especially if you're staying on-point. My husband did that (processed in like 2 days early) and it was no big deal.
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PO!NT OF VIEW - A Different Look at Roller Coasters
http://www.crosswinds.net/~justmayntz/thrills/