Once you've unlocked your bootlader, updating it to the lastest (and presumably greatest) will only updat its code, and not relock it. (If it did that, I bet a lot of the users with trouble could've gotten a free warranty reset! -- ASUS wouldn't do that, trust me.)
For completeness' sake: if you did not unlock the bootloader before, the unlock tool will remain as functional as it would have been in the first place. If you can't unlock the new bootloader, you couldn't have unlocked the old one either (issue is on ASUS' side, well referenced on the forum).
Reflashing an older bootloader: no, unless you have NvFlash and the concurrent backup files-- I didn't gather you ran that procedure before upgrading to .30...
TL;DR: your bootloader will remain unlocked if you unlocked it prior to updating, and remains unlockable if not.
any idea if the reboot to recovery thing is BL-related? if so, would upgrading it solve the problem? or is the tf700 owner's club SOL with that?