New-ManagementRoleAssignemnt takes a long time to become effective

Hi,

I use new-managementroleassignment cmdlet to give an application impersonation permission to service account in our organization. Anyway I found out, that it takes up to 30minutes (average 25), before this permission becomes effective. I run a cmdlet in a same site where are objects that I want to access using EWS.

So a question is: Is there any way how to make this process faster? E.g. result of add-mailboxpermission is effective in seconds.

We use Exchange 2010 SP2 in our organization.

Thanks

M.