GnuCash backup files

[Cristian Marchi]

I've a question about the auto deletion of backup files by GnuCash older 
than X days as set in preferences: does it remove the files based on 
timestamp or by parsing the date in the filename? I've an Italian user 
reporting the deletion of a GnuCash file that he currently used with a 
filename set as a backup file. I was wondering if GnuCash could have 
deleted the file because its filename was composed with a date older 
than X days.
I'll try with an example: let's say my financial data are managed in a 
file named "data.20120101.gnucash" saved last time on 2012.01.01. Let's 
say I have preferences set to remove backup files after 5 days. Now if I 
open the previous file on 2012.01.08 (more than five days later) could 
my file be deleted by GnuCash? And what if the same file with the same 
name was saved last time less than five days before the reopening?

While talking about this feature, when GnuCash checks for the deletion 
of backup files? every time you start it?

I'm sorry if I posted my question in the wrong list but I was unsure.
Thanks for any advice
Cristian