I'm pondering this myself. My two one-gallon batches, already in secondary, have a lot of sediment and I'm considering racking them again (tertiary?). Problem is, one's already almost a pint down, the other a little less than that. If I rack again, how much should I worry about oxidation?
My first batch of cider I added glass marbles to reduce the head space -- something I read in an old wine-making manual. Then later afterward I noticed the marbles were made in China, so now I'm all paranoid about lead. (Not a recommended additive to alcohol, as the Romans might tell you.)
Primary: 19 Gallon (Cranberry) Cyser, Home Alone Cranberry Melomel
Secondary: Tenure Forecast Cider, Riotin' Cider, Virgin Cider No. 1
Bottled: pumpkin ale!, brown ale
Drinking: red ale