For the years between 1970 and 2010, I have seen at least one object from each of those years with the exception of 7 years (1970, 1973, 1974, 1978, 1979, 1986 and 1989). And that's with not even trying to see something from every year! I guess when you've had 125 observations, you're bound to cover quite a few years.
The earliest object I've seen so far is from 1961 (1961-015-C - Ablestar 008). The newest object so far are from the launch of the Shijian-6G and 6H satellites launched on Oct 6th (2010-051-A/B/C/D).