Zevele, just in case it is of help. I have some 30.000 tracks now and adding an average of 300/day.
I tag some of the files with MusicMatch first before importing them to MJ, change the cover art and put the one from amazon.com (the large version of the cover) which in my opinion displays better in MJ cause it's bigger than the one from MusicMatch or allmusic.com.
I import then the files into MJ, go to "recently imported", reverse the seq. order to have the latest first, select the new files and "send them to" a playlist named "tagging works". Then I work on tagging, covers, renaming, genres, etz. This allows me to isolate the new tracks to work with them comfortably.
Optionally, once a complete album is tagged I send it to "Playing Now" "add to end" and n.1 random file of the album to "Playing now" "next to play".
I also have a smart-list named "new releases" which is populated by the "recently imported" playlist with a condition of "number plays" = 0. This allows me to always have a smartlist containing the tracks that I haven't played yet. I have set the "recently imported" playlist to NOT clear after exit.
Hope this helps.
Regards.