Bei http://www.velominati.com ist die Frage schon für Fahrräder beantwortet als Rule #12.
In abgewandelter Form und unter Berücksichtigung der Copyrightregeln muss das also für Uhren heißen:

Rule #12 // The correct number of watches to own is n+1.While the minimum number of watches one should own is three, the correct number is n+1, where n is the number of watches currently owned. This equation may also be re-written as s-1, where s is the number of watches owned that would result in separation from your partner.