Ive seen some photo's of some guy with over 20 Vincents. But he had a part time guy caring for them.
One thing I have noticed with large VMX collections is the neglect of bikes. If you think you can actually look after 50 + bikes your in denial. Just do the math if your 50+ and have another 20 bikes waiting for restro you will die before it happens. Or you need to be very rich and pay for someone to do most of the work.
Spot on.
My bikes live under sheets in an enclosed shed in a dry climate, but they still require care and attention to maintain them, even if they don't get used.
My collection is about half the size it was (and all of the larger projects have been sold off), but there's still hundreds of hours and thousands of dollars to get all of the bikes where I want them...
I love tinkering with bikes, and I particularly love bringing them back from the dead - but it's all too easy to bury yourself in them.
To answer the original question, I reckon that five or more actively used race bikes is a large collection.
Ten or more nice bikes that are shed queens/lightly used is a large collection.
But thirty shitbox "gunna" projects that sit in the shed untouched doesn't really count as a large collection...