personally i have close to 500 kits, not all ww1 aero but 80% are. but i know a guy, hes close to 70 and has been building avidly without a break since the 50s. he has between 3000 to 4000 kits by his estimation stuff he has collected from the start. he is a very prolific builder building 3-4 per month, all 1/72 so its much less involved.