A temporary fix is available for the HTC Thunderbolt dropping its 4G connection! 

Post containing solution
( http://community.vzw.com/t5/ThunderBolt-by-HTC/Thunderbolt-drops-4G-off-and-on/m-p/630690#M7523 )


Props to ChristinaB_VZW Wireless Employee for contributing the "force Rev A" solution. I used it once and currently have had signifigantly less problems.