After the arrival of Marco Silva during the summer, Watford have established themselves in the top half of the standings, with 22 points coming from their first 15 matches.
Watford made 10 first-team signings by the end of August, but Duxbury has revealed that there will be more incomings at the start of 2018.
Duxbury told the London Evening Standard: "We are already identifying targets for January and next summer. We don't stop. The window is almost a misnomer for us. We tend to scout all year round.
"There is nothing to stop you having discussions with clubs. We like to get our business concluded very early, otherwise it is inefficient and inflationary. We have had a quick evolution from a Championship squad [in 2015] to a Premier League one.
"Hopefully, you get to a point where you have a fixed 25-man squad and you're happy with the 11 on the pitch and the cover, so the amount of activity starts to reduce."