The Dink Network

For me, the attractive thing about trilogies as a jumping off point was that they allowed for grand ambitions while limiting the scope of your first d-mod. Given the very high likelihood that your first try is a) not going to be that good and b) not going to be very well structured, planning a trilogy means that you can make the d-mod working towards something while safe in the knowledge that it's a learning experience that won't hurt the later entries too much. I thought of the Friends Beyond modules as a model at the time - the first was short and basic, the second much larger and more ambitious without rewriting the rules for everything, the third an epic with a concept behind it that someone new to d-mods couldn't really have made.

It does seem to be community specific though - from my time playing Neverwinter Nights modules there were definitely a lot of serialised modules but not specifically trilogies. I think the Arithia games probably set a bar that people aimed for.