How long to rescan Media files? Too long?

I have a ReadyNas Duo with 1 off 1TB drive.

The drive is 73% full = 676 GB.

The Media share on the drive is about 100 GB comprising 4 directories containing the following files:
BitTorrent empty
Music 11,126 files in 1384 folders 55.0 GB
Pictures 23,966 files in 1035 folders 41.9 GB
Video 28 files in 9 folders 2.54 GB

Whenever I add a file or group of files to the Media share on the NAS, I have to use Raidar to rescan the Media files before they become available on my network connected media player (a Playstation 3).

This process takes 42 minutes.
I have the following questions:

1. Should it be necessary to perform a Media rescan evey time a file is added to the Media share on the NAS?
2. Should scanning the Media share take this long?
3. Can I narrow down the range of folders I need to scan, so that the process is faster? I have tried doing this by identifying the folder I want scanned in the Raidar Streaming Services ReadyDLNA Folder but it still takes 42 minutes to complete the rescan.

Thank you,

Geoff Minshull

Radar is at version 4.3.3

ReadyDLNA is at v1.0.22