On that media server your modification to the default timeout value is placed in the servers bp.conf
This needs to be reread by the netbackup services.
Restarting netbackup performs this. However, this reread can be done without stopping services.
Issue the command on the media server
bprdreq -rereadconfig -verbose
The command bprdreq is in %installpath%/NetBackup/bin/admincmd/
Two technote references
DOCUMENTATION: What are some of the situations where is it necessary to restart daemons / services in VERITAS NetBackup (tm) 6.0?
http://seer.entsupport.symantec.com/docs/281317.htm
DOCUMENTATION: After making any changes to the bp.conf file on a VERITAS NetBackup (tm) server, is there a way to reread the configuration without having to stop and restart the NetBackup daemons?
http://seer.entsupport.symantec.com/docs/234746.htm