I have them all in 1 B Net and yeah the main disadvantage is the login time. But typically I use it to quickly check my bank alt or any other 2 minute time waster while I login to the accounts.
The other disadvantage would be if your account got compromised somehow, then you would lose all of them, while possible that is unlikely.

Having on separate accounts allows quicker login, and the above account security. But you would miss out if BoA stuff ever became BoBnet.