I haven't yet and didn't previously. Basically i only plan on applying my ratings to races where all horses have had 3 or more runs previously so hopefully that cuts out a lot of the races with younger horses.

I also plan on basing a lot of the ratings on averages and percentages (i.e. API, win %, place %, etc) so that it avoids overweighting ratings to horses that have had 20 wins on 60 runs and is 9 years old vs a better quality horse thats had 10 runs for 5 wins and is 4 years old.

Hopefully that makes sense and I agree that over-allocating 'points' to horses just because they have had more runs due to their age is something to be avoided.