Personally I believe having an open dialogue between buyer and seller, with revisions, is a key part of the collaborative process. The buyer might initially say the want a voiceover to be delivered in a certain style, send your first delivery to their client, who decides they want it to sound deeper/faster/more or less [adjective]. You cant provide hundred of takes of whole deliveries in your initial delivery just to avoid revisions, which could bamboozle a buyer.
Also, life happens. Sometimes a seller needs to extend the delivery. Honestly, if a buyer has said ok and you have a good communication record with them throughout the process, if I, as a VO, have a cold, I don't think it's wise to record audio that is substandard, I would explain to the buyer I am ill and will deliver a few days later than expected because of my illness and recovery. If both parties are in agreement and have an understanding and expectation of new delivery date, why on earth should this be a problem?