I'm with Multibear with this for the most part.

I have my 10 accounts over 2 B-nets (8/2 split) and it bothers me oddly much that I don't have all the same mounts and toys and whatnot on the secondary B-net. I've farmed a few and even thrown a decent chunk at the BMAH just to have a few matching mounts.

I'm considering dropping down to 5 as well, as I'm having a kid so game time and perhaps even money will be somewhat tighter (the main factor being that I don't know if I can justify upgrading hardware just now, which I would need to in order to continue with 10). However, I will definitely be using 5 of the "main" battle.net account, even if I am already token capped on it. As MB said, I too do not want to HAVE TO farm gold. I don't mind farming some gold for fun and getting nice stuff ingame, but I never wish it to be something that is required of me. I'm fine paying for my accounts and have always held the belief that if you can't comfortably do so, you really need to consider whether it's worth it in the first place.