Owing to my sticking with simple forms and virtually no pre-defined designs for 'solid wood' items, when I'm in basic turning mode I only ever have one piece at a time in work on the lathe, rarely do I start a piece that is not finished within the days session.
Blank preparations are another matter, they tend to be done in batches, sometimes a whole day doing nothing else but fill offcut firewood bags for my neighbour.
If you turn up a batch of green bowl blanks for drying do you consider them as in process individual projects or just one project?
Simple Segmented box component parts are usually done in batches as and when appropriate material and machine setup is relevant.
Assembly of parts is likewise usually done in batches but finished turning is always done to completion, never left on the lathe.
Funnily enough I've never thought of anything I do on the lathe as a project, other than say the making of a turning tool that's needed, possibly because since I started turning I've not tackled any complicated or multi part builds that need an extended timescale so just see them as short term tasks.
Currently have four chucks, for convenience could do with another 125mm to get the extended jaw travel, but since Axy no longer market the goliath I doubt it will materialise.
Because of my narrow output style and afore mentioned 'session completion' I do not utilise the facility to leave a piece on a chuck, they're just fitted with differing jaws for quick change of holding method.