Yongbum:
Assigning the EntityList to the BindingSources shouldn't be taking any significant amount of time, unless you've got some kind of eventing going on (e.g., something in BindingSource.CurrentChanged or whatever).
I usually assign my EntityLists to the BindingSources *before* loading data into the lists:
Dim mCustomers As New EntityList<Customer>()
...
mCustomer1BS.DataSource = mCustomers
mCustomer2BS.DataSource = mCustomers
mCustomer3BS.DataSource = mCustomers
mCustomer4BS.DataSource = mCustomers
mCustomer5BS.DataSource = mCustomers
then load the data
mCustomers.ReplaceRange(mPersMgr.GetEntities(Of Customer)())
Using ReplaceRange() allows you to load and reload data as needed witout having to reconfigure the link between the EntityList and its BindingSources.
Nevertheless, I tried it the way you did it against 121,000 SalesOrderDetail records from Adventureworks 2000, and the time to assign the EntityLists to the BindingSources was about .0015 seconds compared to 11.5 seconds to load the data (local database, of course). Must be something else going on.