Insurance Cancellations

Does anyone here actually cancel their insurance when they sell their bike?
I’ve got 3 running policies at the moment and whenever I’ve sold a bike I’ve just let the insurance run out.
I recently heard this was a naughty, but I’ve never had any comeback from doing it.
I currently have two policies with 2yr no claims and one policy with 4years.

I tried to leave a policy to expire when I bought my new bike but they wouldn’t let me transfer the no claims to the new bike until I cancelled the old policy and therefore the no claims on it (the cancellation fee cost me more than the remaining payments on the policy). They wouldn’t let me use the no claims on more than one policy.

I guess yours is a multi bike policy so you can share the no claims?