we had 5 pm flights before... We waited on the ship for a max allowed time, then took a taxi, stood in line to drop off luggage (usually within 4 hours beforehand, but Spirit used to be a lot less rigid about it before the pandemic), then went through security, lounged around at FLL, had lunch, read books, browsed internet... It wasn't too bad. Now there is a 2 pm return flight which we enjoy more.
Found MCO to be a lot more "lounging before going through security" friendly than FLL. Didn't get to lounge at MIA, so no opinion.