Oh, did I hear Netlify there? Are you referring to the build times on your local computer or on Netlify? If you are using the free tier in Netlify then slowing down of builds is something that seems to be some kind of throttling on their behalf. You either live with it or upgrade to a paid tier and it goes back to fast. I have a cronjob running that triggers daily builds on Netlify and those are running smooth and fast. When I develop and upload changes without much time in between they get slower and slower. It’s acceptable because all else is for free.