The Aruch Hashulchan at the end of Yorah Deah 116:3 writes (emphasis mine):
וכמה זמן ישהו שיהא מגולה ותיאסר? כדי שיצא הנחש מתחת אוזן הכלי ויחזור לחורו, והוא זמן מועט
And how much time can the drink be left uncovered until it becomes forbidden? Enough time for a snake to come out from under the handle of the vessel and return to its' hole, and that is a short time.
While still not giving an exact timeframe, the Aruch Hashulchan is at least clarifying that it's a relatively short amount of time.