Personally, i find stopwatch to be rather out of the line. An item sitting on 600g regardless if it gives no stats at all except for the active, has become a core item for all lanes due to the strong outplay potential it offers aswell as the possible build paths it leads to.
Definitely, it’s a one-time use and it only redeems 180g if one does not plan to upgrade it to a legendary item. Nevertheless, the point is that for its low cost the active is too powerful since it shares the same stasis duration with zhonyas hence making it all the more impactful in the early game where 2.5 seconds are significant in said situations like under towers, near large combined minion waves and early roams/dragons.
Coming into a conclusion, my suggestion is that its active duration should be reduced to a maximum of 2 seconds with 1.5 being more optimal although the latter would make it rather a situational purchase.