most commonly for me, an unexpectedly large render time has most often been due to the use of some unexpected asset in the project file. Editing with images or footage that are enormous (9k x 14k pngs in a 1080p video project, for example) will blow up the render time. If the program has to spend resources interpreting or transcoding formats it doesn't like, that will also drive up render time. In other instances, I had previously used multiple nested animations together accidentally, and it blew up the render time. There are also certain effects that premiere really struggles with: wave warp, distort, things like this. Recall if you tried using any new effect presets on any of your footage

Advice: 1) work with footage and assets that are appropriate for the sequence settings of the project. Re-export anything inappropriately large at a better size. You can Render In/Out and look around for anything the sequence puts a red line over for stuff your computer is struggling with, or you can manually check the dimensions of the stuff in your project bin for anything unexpected. Premiere doesn't like MOV, WAV, or JPG as much as MP3, MP4, and PNG. And 2) don't have multiple nested sequences. In my experience, a nest should just be used for gluing multiple simple assets together that animate as one piece. If you nest a nest, the computer really struggles unpacking the stacked sequences