More than two decades, in fact, though most of the earliest stuff was on borrowed accounts–I don't think I had my own email address until twenty years ago next year.
The funny thing is that there are people I know from my very earliest ventures on the 'net with whom I still cross paths.
In no particular order:
Steven Grimm, who is now a member of Facebook's infrastructure team working on memcached (which we use very extensively at Ironic Design) was very active in the Atari ST community back when I was first getting on the net.
Howard Chu was, if I remember correctly, responsible for both the largest FTP repository of Atari ST freeware up at terminator.cc.umich.edu (for which I used to know the IP address, because DNS was not reliable in those days), as well as handling the porting of the Gnu C compiler to STOS. This is what I learned to write C in. These days, he is the primary coder on the OpenLDAP server (which we use very extensively at Ironic Design).
David Parsons (orc) was part of the community when I started reading newsgroups, and worked on the STadel port of the Citadel BBS software to the Atari ST. I ran across a reference to his C reimplementation of the Markdown text-processing language.
Now my current connection to orc is more tenuous than the others, but the idea that these people I have known of for twenty years are still involved in software that I used and depend on on a daily basis…it's kinda weird.