Moving users from EV 9.0.3 to EV 10.0.3

Dear's,

I have EV 9 installed in my environment with exchange 2007 and have planned a seperate EV 10 infrastructure for exchange 2013.

I do not wish to upgrade existing EV 9 to EV 10 as it involves upgrade of windows also.

For migrating users I am planning the below steps:

1. Disable archiving in existing EV infrastructure.

2. Move mailbox to exchange 2013.

3. After 2 weeks enable archiving in EV 10 infrastructure.

4. Move archive from EV 9 to EV 10

My worry is between step 2 and 3 there will be a gap of 2-3 weeks, during this period will the users whose archiving has been disabledin EV 9 will be able to acess their old archives from outlook and OWA 2013 after their mailboxes have been moved to exchange 2013.