The Seagulls prepare to face off against the Toffees on Saturday high in confidence as they are unbeaten during their previous seven games.
Duffy said: "I don't think there is ever a good time to play Everton away.
"Their home record is quite good. You look at the players they have and the money they spent this summer, it's going to be a tough game.
"I know from playing at Goodison it's a tough place to play at. When the fans get behind them there's probably not many better.
"But we are flying. Nothing can really stop us at the moment. If we keep playing like we are I don't think many can stop us."