1990's is when the internet could be used as a trolling device. That's >24 years ago (Most likely closer to 17).
Saying its been a long or short time is really arbitrary, if we compare it to when electricity was invented it would be represented by the ratio of 0.065. If you compare it to someones life that was born at the same time that internet was used for trolling then it would be 1.0. If you used the beginning of human existence it would be 8.5x10^-5.
It's really just relative. I however am thinking about the future of trolling and its expansion and continuation which is unknowingly big therefore how "new" trolling is, is just relative.
Sorry for any previous confusion, didn't really explain myself.