I was just able to link two more UO accounts to my second EA Account, pushing the total number of linked accounts for that account to ten. (They were two old accounts that actually belong to a friend although I made the payments for her for quite a while. She stopped playing a few years ago and I've never been able to get her to play again for longer than about a week. Don't think she'll ever come back now...too hooked on WoW.)
Don't have any more UO accounts to link (thankfully), so my testing on this issue is done. Anyone else still wondering how to allocate their accounts among e-mail addresses might want to submit a question to support (support.ea.com) and ask what the maximum number of linked accounts is at this point.