I too follow the n+1 mantra.
Until recently I was at 13 bikes, only two of which were street legal. When my Sprint was totaled (down to 12), my wife decided to sell her Ninja 400 since I wasn't planning on getting another street bike (down to 11) right now. Then a friend listed a TTR-90 for only 750 and couldn't pass that up (back to 12)
The current stable:
Mine:
2007 SV650 - Primary race bike with engine work
2006 SV650 - SS class race bike
2006 SV650 - track bike I built for my son***
2005 SV650 - slightly upgraded parts, replacing the son's track bike
2008 GSXR600 - track coaching bike (Sport Rider Coaching)
2014 Ninja 300 - ULWT class race bike
2015 Motrac MX125 - TMGP endurance bike, 'A' bike (Grom clone)***
Hers:
2015 Ninja 300 - track bike
2015 Motrac MX125 - TMGP endurance bike, 'B' bike***
Others
TTR-90
TTR-110
KLX-110
Getting ready to sell the bikes with ***, so that will put us in the single digits for the first time in 2 years. And yes, I know I have an SV problem.