Take the beetles out after about a month and put them in some new bedding. Keep the bedding because the tiny worms are in there. Every 4 weeks or so you can change out the bedding and keep it till the worms get big enough to feed to your geckos.
Mine are growing at a steady clip at 70 degrees. I use one of those 3 drawer sterlite organizers you can get at walmart for 10 bucks. Bottom bin I have the beetles. Every 2-4 weeks I separate out the beetles, but the substrate in the middle bin and put the beetles back on new substrate. When the babies are visible I move them to the top drawer which is where I dig around in for feeders.