Two Problems

Hey Folks 
I am trying to solve two problems. I am in the last stages of delivering my doc and I am basically going thtrough and  creating stereo files from mono files for my QC. I am working proxy preffered and still getting spinning rainbow of death regularly. Which causes me to force quit. lose all my changes because FCP only backs up every 15 minutes. Second issue can we adjust the back up from 15 to 5? or 3? I am getting desperate here and I am running out of time. 
Help.

First of all, leave mono files mono, duplicating them doesn't make them stereo, and risks cross-phase issues. They'll still be mono audio.

FCP "saves" more often than every 15 minutes, the "back ups" are done about every 15 minutes. You can not adjust that yourself.

What macOS and FCP versions are you using?
How much RAM on your system?
What "percentage" of your system drive's capacity is left as free space?
How long is your project?d

I'd start by deleting all the render files for that Library, and deleting FCP's pref files.

Backups for Final Cut Pro (in the App Store). You set backups to run whenever you want. Note: I have this and use it but have never needed to retrieve a backup.

All that Ben and RevJimBob say.

Not sure about your setup but even if you work in proxy preferred, if you have a slow drive holding all your original clips and that drive is connected then you can run into the beach-ball problem. FCP hasn't actually crashed but just needs a long time (very long sometimes) to do what it has to do on that slow drive (my guess is managing the database, but really no idea .
I have the same problem with following workflow: Original media stored on USB-3 drives. Proxies generated onto fast internal or external SSD drive(s). If I have the USB-3 with the original connected and even though I'm in Proxy Only or Proxy preferred mode FCP can go, e.g. after I change something or select a diff Event, into the beach-ball spinning for quite a while (large project). If I disconnect the USB-3 and only have the proxies on the SSD(s) connected all is good.

If that is not your setup, never mind

Thanks for the help folks!!! As it turned out the issue was the sound editing plugins I chose to use on this project do not actually play well with FCP. So with some tenacity and patience I set the whole project to proxy and manually went in and removed the plugins from each of the sound clips and the problem is gone.
Thanks for all the great responses.

What audio plugins were they? Could help someone else in the future avoid this.