Can't put a single number to it.
Level of interest and priority is high, time available is short.
Level of expenditure shows commitment but output does not justify it, the only justification is pleasure.
Amount of available time spent on Model Engineering extremely variable.
An accumulation of Model Engineering interests has lead to a large collection of 'under the bench projects' waiting their turn.
It will be completed 5 to 10 years later than expected.
Hmmm, I have heard of business models, maybe I need a hobby model?
Nigel