GarageBand 'audio resolution' in 'advanced' preferences

Further to my recent post re GarageBand suddenly quitting while recording a radio broadcast because 'file had exceeded 2GB limit' (or something to that effect), even though I had set it to 80 bpm which should have given me over 5hrs of recording time : nevertheless it carried on recording when I clicked the record button again.

I had selected 'Best' from the Audio Resolution drop-down menu in the GarageBand Preferences tab. Would this have any influence ? I do want the best recording I can get, to burn to CD. Is it necessary to select Audio Resolution before recording, or is it something that can be selected after recording ?

The next part of the Ring Cycle I am recording is this afternoon, so would be grateful for any solution that would prevent GarageBand unexpectedly quitting again, before then !