Juan, I'd say you kinda HAVE to keep it forever now. You have a lot of money in it now, but remember you have a lot less in it then the person who bought it new!!
Enjoy it and try to see the big picture... Years of enjoyment with a car you love. It's a beautiful thing
You're right, why sell it now and let someone reap the benefits of all you've invested?
As stated earlier, always be leery of low mileage cars. They tend to have been sitting and that is hard on cars...
-Grant