Preventative measures when Apple stops signing

Hello Chaps

I’m a complete newbie on the Apple TV JB scene. Managed to pick one up from ebay and jailbreaked it today on my macbook pro (although i did read people having problems on mac’s and resorting to windows to complete the JB).

Anyway. I’ve got an untethered 5.3 JB. Installed XBMC via Terminal.
However, I wondered what happens when apple stops signing 5.3?

If for instance my apple tv develops a fault of some kind and I need to re-jailbreak it, what preventative measures can I take now, to ensure I will keep the same software version, in the event that I have to reinstall the 5.3 ispw instead of being forced to install the latest version which apple are signing at that moment in time?

Hopefully this makes sense?