Exporting takes an entirety

Render time depends on the composition more than the machine. When I design complex composites with lots of layers and nested comps I keep an eye on the render time per frame. When a full-resolution preview takes more than a minute a frame I start redesigning the comp to speed things up. When the render time looks like it's going to take more than a few seconds a frame I'll almost always render an Image Sequence that I can drop in Premiere Pro and add the audio track, do final editing, and polish the color grading. I almost never create a composition that is more than one shot and most of my shots are less than 7 seconds because most shots in a movie are less than 7 seconds. When I comp is going to take longer than 2 or 3 minutes a frame, I send the comp to a render farm to have them render the project.

I never edit movies in After Effects. Doing so is asking for a render failure and adding frustration to your life. 

AE renders a frame at a time by default so 20% of the available ram for a 4K comp with a fair amount of effects is pretty standard. If you added a single effect that does not support multi-frame rendering, then enabling the option in preferences (Alt/Option + Ctrl/Cmnd + ;   (Page 13 Memory and Performance)) will not improve rendering performance while that layer is active. 

I hope this helps.

Without any info about the project and its contents we can't tell you much. A single effect can slow AE to a crawl, given that even today it barely uses actual multithreading and parallel processing or GPU acceleration in a sensible way. That notwithstanding there's an issue/ bug where rendering stuff to certain formats and via AME will take forever, so the first thing to try would be to render from AE directly in one of the supported formats.

Mylenium