My retic was underfed, so she grew really slowly. She was in a tub (I'd have to check the size) for most of the time I've had her, until she hit 4'-4.5'. I moved her into her 4'x2' in December, and she's already outgrown it. At the rate she's growing, she'll outgrow her 6'x2' before I can even get her in it. I'm hoping to have a Herpstat in by end of September, but I may just have to temporarily get some more Hydrofarms, because she appears to be 7'-8'. I can't get her 8'x4' this year because it takes so long for the cage to be built and shipped out, and I plan on moving by the end of the year. She'll be turning 2 years in about 2 months, so she's actually a couple feet behind in growth, but she was fed fuzzy mice every 2 weeks for the first 6 months of her life, so she got a slow start. So, yeah, they grow fast. I wouldn't even count on a year being long enough for your 4'x2' to last unless you got a hatchling, or a super dwarf. Then maybe it would last you 2-3 years, or life if the snake stays small. I hear a pure male tops out at 6'-7'. I don't know much about Burms.