I think you may have answered your own question. With deciduous trees, the consensus is to leave layers in place through the heat of the summer if possible, particularly if the presence of adequate numbers of new roots to support the layer is questionable. I don't see why this wouldn't apply to JBP. The other side of the coin is that you must keep the rooting medium consistently moist throughout the process.I have a few JBP air layers which have been successful. Should pot these up or wait for cooler weather. I worry with the heat in Sydney they may dry out if I can't water them in time.
Can we see the whole thing please? Never seen a JBP airlayer myself.
Thanks for the advice. As you mentioned it was quite difficult to remove the spagnum moss. Here are a few pictures.When you decide to separate, new roots are incredibly brittle so best to just pot up as is. Only try to remove moss if you can be very, very careful. I usually just pot the ball up as is then repot again the following spring. By then the roots are much stronger and can be manipulated safely to get rid of the moss.