Herman,
I personally prefer not to add a second drive because it will split the track location references in the library and you will have to backup to two drives which is inconvenient. I would rather buy a pair of bigger drives and copy everything on to a single drive. HDs are really cheap. You can get a 750G Seagate for about $250. Unless you are doing everything in 24/96 uncompressed, it is going to last a long time.
I personally prefer not to add a second drive because it will split the track location references in the library and you will have to backup to two drives which is inconvenient. I would rather buy a pair of bigger drives and copy everything on to a single drive. HDs are really cheap. You can get a 750G Seagate for about $250. Unless you are doing everything in 24/96 uncompressed, it is going to last a long time.