It really depends on the type of race, distance is not always the limiting factor. Here in socal where crits dominate the racing scene being able to ride 100 mile days or 300 mile weeks have very little bearing on your performance in a crit. Since I have been training for crits I can ride 45 minutes to an hour hard and that is more important than riding 4 - 5 hour training rides.

Of course that is why we have periodization, the beginning of the season is for good base miles (the 60+ mile rides) and the build and race periods are for fast and hard workouts that may only be 20 miles long...

Only an individual rider can tell though if they are ready to race, no amount of training can tell you what to expect out on the race course... now if your race is 35 miles (typical cat 5 road or circuit race) and you can only ride 25 miles straight then you are not going to be ready. Right now I can ride easily 40 miles straight without getting off the bike, but I would get distroyed in the hills... see what I mean?