You could wait until then and get darts but I mean a 36 x 18 x 18 inch terrarium is going to cost a bomb to set up for darts and keep in mind it will need a few modifications, finer mesh, sealing the gaps in the doors and some glass on top of the screen. If you're beginning with darts you'd probs be best getting a smaller viv and a custom one designed for darts. I'd personally get another tomato frog, or even 2 more as you could easily fit that amount in that size of viv and just install a 2% UVB tube inside.