Renaming albums causes problems in iTunes

I'm having two major issues with iTunes for Mac

1. I manually add album artwork. All that shows up is a white square. I restart iTunes and the artwork appears.

2. I have a double-disc album that I'm importing. It will sometimes show up as two separate entries:

JOHNS ALBUM (DISC 1)

1. Song 1

2. Song 2

JOHNS ALBUM (DISC 2)

1. Johns Song 1

2. Johns Song 2

I edit the info in Itunes and remove (DISC 1) and replace it with Disc 1 of 2, then do the same for (DISC2). The two discs merge into one entry, like I want, but all of the songs on Disc 2 are "missing." I restart iTunes and they show up.

Why do I have to restart iTunes so much when doing basic file editing?!?