photo is an airlayer on CDDN started for a friend for trade. just starting to see roots inside container. i guess this should be pretty root bound before dividing?  This is my first airlayer. will start ones on cddb and black madeira today also.

Yea. Let it get a little root bound so it comes out in 1 piece and doesn't break apart. The more roots it has the less stressed it will be when you cut it off.

Jason said it all.

enough to support the plant

Good comments.

Part of knowing when to take an air-layer is based on climate and facilities. If you have the shade and can provided the humidity, any time there is sufficient roots,is a good time. If you remove the air-layer, and cannot provide a TLC type environment, then hot summer weather, and possible low humidity will work against you.