Whilst agreeing with t566 on the wisdom of spending vast amounts of time in the A3 lounge, you would not actually have to pass through security - both the A3 & LH lounges are pre-security in the Schengen area. You are travelling to a non-Schengen country, of course, and would therefore need to eventually clear the central security for those gates to access the contract lounge A3 uses there, but there is no earthly reason why you shouldn't take your luggage into the Schengen lounges whilst you wait - just tell the people checking the boarding passes what you're doing.

This does assume, of course, that your immigration status allows you into the Schengen zone ...