I rack and rack and rack until there is no sediment at the bottom at all - not even a dusting. Because with my luck, I move the carboy the wrong way, and whoosh! It's all mixed in with everything.
It takes a lot longer this way, but since I'm bound to mix or directly stick the racking tube
IN the sediment, I just rack off a couple of times more.
I top off with a similar wine.I ususally don't need too much. I have a small trick to make sure you rack the least amount of sediment off your wines:
I put my carboys on a sort of a tilt in that I put it on the ledge of my wine-table (the table has a a raised edge, so nothing falls off). That way, all the sediment naturally falls down to the lower side.
When I am ready to rack, I turn the carboy slowly around and stick the racking tube to the lower side (which was the higher sidebefore), where there is practically no sediment.
It's a great method for me. And, it's easy to do.