My mainland male retic hit 7 feet in his first year. He's now 15 months and easily pushing 8 feet. They grow quick! He's in a 72x30x18 Animal Plastics cage. While he doesn't do much in the day, at night, he uses every inch of his cage. He could probably still be ok in a 48x24x24, but it looks like he definitely utilizes the extra space.