I flew from EGPA Kirkwall to EKEB Esbjerg yesterday. During the climb to 25000' I reached 8000' and the speed crept above 250 knots. Control promptly told me to reduce it to 250 kts which I did. I continued to gain height passing the usual trigger of 10,000' but control did not lift the speed restriction.
By 16,000' I was fed up with this so I increased to 350 kts for the rest of the flight and received no speed restrictions until the later stages of the flight.
I don't know what criteria is used to trigger the speed instructions but in this case I seem to have dodged a bit of them.

John