When I bought watches on a whim, I also got desillusioned and tired of them. With learning the "do Your research etc. stuff" I´m already in love for 8 to 10 weeks before even buying. Well sorted quantity (40 to 60) does have a lot of privileges: none gets too much use so all of them do work; it´s difficult to get tired; it´s easy to always fall in love again after a pause. Less than 15 nowadays sounds like sacrifice.
If money, space, time spent etc. are of no importance: a minimum of three and maximum of twelve (per brand ) is a good housenumber imho. Usually every 2-3 months I´ll pick some others to wear several weeks in a row, together with the favourites.