Given that Lewis was only ever on the floor twice and denied the right to fight on in one of them i'd say it affects him very little. Look at all those good fighters and punchers he beat without ever being dropped. As for the 8th, he's got plenty of stoppages from 5 to 8. He's also at a slight disadvantage via this exact criteria due to the modern day being 12 rounds. Also, nobody has ever stopped Lewis after the 8th either. He has also never lost a fight that went past 5 rounds, so not stopping anyone after the 8th was sure no disadvantage, he won every one of them.