With Windows PC's/Laptops, I used to completely format and reload Windows on a yearly basis as it would get progressively slower. I haven't had that issue with Mac OS. However, I do wonder... is it best to backup everything, format, and install High Sierra from scratch, and then re-setup everything? Does anyone see any noticeably improvements from doing it? My MacBook Pro is running fine at the moment though... except the occasional graphics corruption usually meaning it is due for a restart (I just sleep my MacBook pro all the time, and only restart when really needed). Thanks.