I have one rule with all my bikes I buy, If I can't turn it into a rider in 6 months it goes, the only bike I will never sell is my 1980 PE175t that has been in the family from new & gave me my start in vmx 6 years ago, you think if I was to keep a bike it would be my RM125T that I won a NZ tile on two years ago, but I have been there done that & now it off to your side of the pond to live, what keeps me going is having all my bikes ride-able and not just doing vmx, I race a 08 RMZ250 in the vets, ride a twin shock trails bike for fun & I now have wife into it with a touring bike which we both enjoy.
I have 8 bikes in the shed & you can ride any of them, but they are all on going projects as they will always be.
So what am I saying, have as many bike as you like to build to ride or what ever but make time to ride with your fiends & enjoy what bonds us all together.