Burmese pythons grow quickly, too.
Three of us split shipping on 3 Burmese hatchlings from the same clutch of eggs. At 14 months, my female was 6 feet long. The other two snakes were over 7 feet. IMO, a 4x2x2 cage would need replacing in about a year.
By the way, a lot of cages for big snakes have no way to keep you separate from the snake at feeding time. A stupid feeding accident with a 2 year old (or older) Burm or retic can be life threatening. Just something to keep in mind.