You haven’t given us a base level of information. If you are going to ask for help, we need to know more detail than what you’ve offered.
Present Render Outcomes: How long is too long? Minutes, hours, or days? You haven’t said – yeah? How long IS your Project? What format is your Media and what are you rendering to?
Project Setup: Match Media to Project settings OR, this is what I do, Match Project Settings to Media
Regressive Testing: Start removing Events or FXs and rendered until you find the Culprits.