Had some advice that with OSR you should extract when can turn the frame flat and shake and nothing if you have a refractometer you could also check that water % is below 18.
Not an expert but sharing advice from one of the longer serving beeks in Kent on how he handles OSR.
When the flowers in the rape fields start to turn green, check the honey frames to see
if it is ripe. Shake off the bees and lay the frames flat in your hand over the top
of an up turned roof, shake 3 or 4 times down. If no honey falls, take and
extract before it gets cold. Do not wait for the frames to be sealed, if the honey
shakes out it is not ready to extract.
Credit to Roland