Switch to Figma.
Honestly though - this is one thing I don't miss about Sketch... Local files and sluggish performance on larger project files.
I literally came here to make the same joke. Not even a joke though, figma is great for this reason and more.
Can you backup your design assets with Figma? E.G., what if you logged in one day and an important file was missing, how would you handle this? (I’ve never used Figma, I’m curious how people think about this for a web service.)
you can export .fig files - https://help.figma.com/article/205-exporting-to-other-tools
what if you logged in one day and an important file was missing
I'm really not sure if that's possible. I certainly haven't heard of this ever occurring, and the community is pretty active with talking about issues.
I didn't find the vague suggestions in this article very helpful.
Here's a few other resources that describe effective file optimization techniques:
https://designplugins.com/sketch-clean-history This works a charm for me
Get a bigger hard drive.