Can I convert serialized inventory items to non-serialized?

Hello,
When we went live with NS it seemed like a good idea to setup some of our higher valued items as serialized inventory. Now that we've been running for a few weeks we quickly learned that there is very little return on all the effort it takes to move these items through our different processing locations.
We'd like to convert these items to non-serialized items if possible. My concern is what impact this may have on the inventory valuation.
A little background info to help in addressing my concern above...We essentially "loan" our units to customers when they pay for the service we offer. When they cancel service we require they send the unit back. At this point the unit is fully depreciated and we receive it back with a $0 value. As a result, our inventory is a mix of units valued at full price because they are new and units at $0 because they are used. The individual unit value is assigned/stored at the serial number record. Should also note that we can't tell whether an item