Everytime you shift...it costs you up to 2-3/10s... so the majority of folks get to 2nd gear and leave it there.. thats why the gearing and powerband is sooo important. most autocross courses don't much go over 60mph... but its nice to have the extra gearing to surpass that if possible, achieving it with A) taller tires... or B) With a raised rev-limit.. mine is set at 8k which renders 64.2 mph.. which should be plenty to be able to just leave it in 2nd gear.
Bill