Question regarding converted GL balances and Annual Close

I have a client who is doing a new install of E1.  They are converting 3 years of historical financial data.  It's been a while since I've had to deal with multiple years of data, so I'm asking for some help with this one. 

The current plan is to bring over a year at a time, run the Annual Close and repeat for each year.  What is the best way to handle this as far as retained earnings is concerned?   They already have retained earnings balances for these years,  so we can't have new entries being created.

Any help will be most appreciated!