I wouldn't upgrade yet. The general rule I follow is that once the snake is longer than the length plus width of the enclosure, then it is time to move up a size
thank moppet.the guy at the reptile shop said its ok as long as there is plenty of hides.but then he also wants to make money.so you think she'll be ok till shes about 3 foot long.
Most of my corns are in vivs that are 2ftx2ftx18".They all seem happy enough I do make use of Vertical space;'Trixie Tables'of Amazon,Fake plants from Dunelm Mill and I also use Java wood Parrot perches bolted through the viv.These are all very reasonable to buy-a lot cheaper than reptile specific accessories- and give the snakes lots of 'extra'space. climbing also helps to keep them from turning into snake shaped slugs whatever you chose enjoy setting up your new viv when the time comes-every month when I do a total clean out I change the furniture around or add new stuff/take out old-keeps them stimulated