I've looked through the wiki and tons of forums to try and find out. How can I filter unit auras based on duration? I know how to create a white/black list, but I haven't seen any filtering examples that hide/show an aura based on its duration. My goal is to limit buff display on player to only buffs that have less than a minute left, hiding everything over and buffs with no duration. I'd also like my debuffs to show only ones with no duration or duration less than a minute.

This is not the place for questions, you're better off asking in the subforums over at wowinterface.
However, I will answer your question.

If your goal is to only show buffs with a total duration less than X seconds you can use the CustomFilter override for auras. The 10th parameter in CustomFilter is expriation, which shows the time when the aura will expire. If you remove the current time from that (timeLeft = expiration - GetTime()) you get the total time until it expires. If I remember right, expiration will be 0 if it has no expiration.
https://github.com/oUF-wow/oUF/blob/development/elements/auras.lua#L162-L171

If you have further questions, please use the forums instead.