Race the final championship race again?

after a couple of championships i had to race the long horizon championship race. that just happen a secound time again. now i complete the races in every city and called back to the horizon place, but no more long horizon championship race comes on. is that long race just there for two times? why can’t i play that long race as often and with a car i want to?
or maybe it comes after i complete a championship at all 6 cities when i called back to horizon place and not just the first and secound time.
it would be nice to drive a longer racetrack like nürburgring in forza 5 instead of doing a lot of short tracks.

Unfortunately, yes.