Looks like you can get a half decent deal with "Six Flags Plus", with access to all parks for $90/per person per season.
Its $20 upfront, plus $8-$10/per month (depending which park you buy it at) and you need to keep it for at least 12 months.
If you get it June 2024, and extend it till Sept 2025, you get two seasons while paying for only 16 months. (i.e. $10 x $16, + $20 = $180 for two seasons). This compares to $30-$40+/for a daily ticket.
*You can purchase these online but you need to pick up the passes for the first time at the park you purchase that at. It's unclear (1) whether you need to pick up new passes each year and (2) if the inclusion of free parking is only at the park you purchased that at, or all parks). Also note that this monthly membership fee auto renews till cancelled.
