The first 900 series was bowled in 1997, since then it's been done at least 6-7 times. They took weight out of the pins in the late 90's to increase scoring and generate intrest in the sport. Also, the bowling balls used today are so advanced from what was used just several years ago.
Case in point, I'll use myself as an example...I used to bowl quite a bit in the early 90's..carried a mid 190's average, high game was 288, series was 730. I used to bowl at least 2-3 times a week, and I was one of the higher averages in the leagues i was in. Quit bowling around 2000. Came back last year, and only bowl once a week. My average is over 200, have had a 300 and a 290 in two years, and have had 4 series over 750 in that time. At my 202 average, i'm not in the top 5 of my league i'm in. Amazing what new tech equipment and a 2 ounce reduction in pin weight can do.
Thats pretty good 4C! I mostly bowl now as an excuse to do this:
