A few months ago we implemented Exchange 2010 with the help of our LTMs. However it has come to light that people have been complaining about how sometimes they are being prompted to log in after they've been logged in all day. What they don't understand is that when they switch between networks "Wired to wireless" or vice versa, their IP address changes so the CAS server they land on is likely different, prompting them to re-authenticate. I don't suppose there is an F5 solution to stop these password prompt. The best solution I came up with was to run Outlook anywhere and do the persistence based on cookies.
Something's amis here. What version of LTM are you using, and have you followed the deployment guide? There are a couple of errata items in the 10.2.x guide, one is to use an small iRule to disable OneConnect for Autodiscover service requests - this is something that is likely causing authentication prompts for Outlook users. Can you check to see if it has been implemented in your environment?