They need to be large enough to survive on their own of it rains....First step is to gradually harden them off to the outside air when they are large enough(this keeps them from damping off). I have not grown these so I dont know the time frame of when this should be done

I have some recurvata seedlings and they are slooooow growing. They are also pretty hardy, so I put mine outside a long time ago. I wouldn't be in any hurry to repot them until they are much bigger. They are epiphytes so giving them more dirt doesn't really help.