Ae crashes every time I save and refuses to play my preview

I am having the same playback issue. I get about 1–2 minutes of caching and navigability, then a pinwheel. I've rolled back versions, reduced other media files on the drive, moved the project file itself, relocated the cache, reset preferences, and adjusted memory to render one frame at a time. 

It fails every single time.

Similarly to yours, this is a 1.5-month-old project with 6-7 days of animation, so pretty killer. Is anybody else having this issue?

If it only happens with one specific project and opening the project with the Caps Lock turned on does not get you started on a solution, we need system specifications and AE version before we can make any suggestions other than "try installing the latest build or maybe rolling back a version."

If you can get the project open with the Caps Lock on, or you can successfully import the problem project to a new one, go through all of the layers and turn off all of the effects. Then go through the project one layer and one effect at a time until you get a crash. That will tell you what effect is causing the problem.

You may also have problems with the footage you have imported. Try moving your source footage to a new folder or adding a special character to each resource, then open the project. If it opens with missing footage, start re-linking the footage in the project panel, one clip at a time. This will tell you if the footage is corrupted.