Botting 20~ hours a day is silly, and will indeed count against you if you are investigated.
Are your accounts all on the same bnet, or linked in any way? If so, that will make it easier to take them all down should one be reported and banned.
Accounts are mostly caught though player reports, although the automated systems that detect loot per hour / kills per hour / straight hours logged in can lock and flag accounts for investigation. When this happens your accounts are reviewed, and matched against a certain criteria. Should your account meet some of these negative criteria (longest login time, kph / gathers per hour, total monster kills, gold gained, quests completed compared to character level, ect), you can be locked/banned.
Theres a lot that goes into investigations when an account is reported. If you want advice, I would def cut down on the botting time for each account. Nobody farms for 20 hours a day, every day. period. Just be safe and always have a way to make it seem like you were in control of the account just in case you do get reviewed. Not going to 100% save you, but it will make you not look as bad.
hope this helped.
