Concur with Horwood and draughtsman99 . Self locking nuts , whether Nyloc or all metal can only be used once in primary control or critical bolted joint applications . They may be re-used elswhere provided that their locking ability is still intact . Indeed Nylocs should only be used in cool areas as the nylon does melt out releasing the nut ! Having said all that , as previously stated , ALWAYS follow what the aircraft manufacturer says in the AMM and IPC !
VK