cut-off time for rsync ?

[Simon Hobson]

> The goal was not to reduce storage, it was to reduce work.  A full
> rsync takes more than the whole night, and the destination server is
> almost unusable for anything else when it is doing its rsyncs.  I
> am sorry if this was unclear.  I just want to give rsync a hint that
> comparing files and directories that are older than one week on
> the source side is a waste of time and effort, as the rsync is done
> every day, so they can safely be assumed to be in sync already.

I thought something rang a bell ...

From the man page :
>        -I, --ignore-times
>               Normally rsync will skip any files that are already the
>               same size and have the same  modification  time-stamp.
>               This option turns off this "quick check" behavior,
>               causing all files to be updated.

As I read this, the default is to look at the file size/timestamp and if they match then do nothing as they are assumed to be identical. So unless you have specified this, then files which have already been copied should be ignored - the check should be quite low in CPU, at least compared to the "cost" of generating a file checksum etc.
AFAIK there is no option to completely ignore files by timestamp - at least not within rsync itself.