When it comes to bikes there is a simple mathematics rule that applies based on the Velominati rules.
Rule N°12 implies:
While the minimum number of bikes one should own is three, the correct number is n + 1, where n is the number of bikes currently owned. This equation may also be re-written as s – 1, where s is the number of bikes owned that would result in separation from your partner.
Source: What is N+1 – NX Trails
I’ve owned several bikes in the past: from a Specialized race bike, a cinelli fixed gear, to an Achielle city bike, Mountainbikes, CX bikes and so on…
I can honestly say that that owning multiple bikes make me happier in life, for the simple reason that all of those bikes are designed to be used for a specific purpose, season, ground condition. When I was riding my race bike I felt limited when I passed a cool kinda muddy gravel path and could not ride that. When riding a mountain bike in my region I felt a bit stupid that 70% of the track was on asphalt, … So every specific bike that I owned gave me more limitations than opportunities.