There are other benefits to maintaining separate Membership Rewards accounts, such as multiple Points Advance and Points Purchase allowances. On the other hand, there are promotions which require a minimum transfer to earn a bonus and with separate accounts your points balance may be divided into inconvenient piles.
If there is a big one you can always ask them to merge the accounts. There is no charge and E-Z to do. Or at lease so I was told by the PLATINUM MR desk.
