As you know, time machine runs backups every hour. But after a bit (a week maybe), it keeps only daily. Eventually only weekly. I want to run backups every 15 minutes and keep them for a month. I'm a software developer and I want to be able to roll back to specific times on my machine, not just the times I check in and out of our code repository. I have a 6-terabyte thunderbolt drive for time machine, so why not use it? Thanks for your help! ---------- I do know how to change time machine to make more frequent backups, it's stopping time machine from eliminating them as time goes by that I don't know how to do.