I'd only use about 25% of my machines on a fairly regular basis, but mainly because 50% of my machines I can't get to easily. The other 25% are things like portables, kids machines & things like the Pixie-Grippa & Good News gramophone.
Having said that, the only machine I can think of, that I haven't played in the last 12 months would be my Peter Pan, and that's because I'm yet to find a soundbox for it.
Then again, if it came down to how many machines I use at least once a week, but every single week of the year without fail, I'm down to only 4 machines- 202 Re-entrant, Amberola 30, Home B with Triumph horn, and Standard B with cygnet horn.
The Amberola 30 & 202 are the real work horses though thanks to youtube
Up until Sept/Oct last year, I would have included the C19 too, but since then it's had new purchases playing musical chairs in front of it, in the front entry
