Under normal circumstances, if Tiny Core works first time, it will work every time. The only time it is likely to fail, is when you have a genuine failure in the computer, such as a hard drive failure. Failure will occur so rarely, that when it occurs, you could replace the hard drive and reinstall.
Tiny Core is frugally installed. The operating system and applications, are read-only. The files do not get modified. The filesystem does not become corrupted like conventionally installed operating systems.
If you backup any important personal data, you can recover that.
If you are concerned, you can save a copy of Tiny Core (or Microcore), and extensions, but failure will occur so rarely, you are unlikely to need them.