RAC & Failsafe :: RMAN Duplicate Taking Long To Finish

How can we tune our RMAN Duplicate as it was taking 10+ hours to finish. Current production database size is 800GB. Approx duration of rman online backup (FULL, including archived logs) is 4 to 5 hours.

Here's the rman backup script we used:
sql 'alter system archive log current';
list archivelog all;
run
{
show all;
report schema;
backup database plus archivelog delete all input;
}
exit

Here's the rman duplicate command we used:
run
{
set until time "to_date(to_char(sysdate,'Mon DD YYYY') || ' 02:30:00', 'Mon DD YYYY HH24:MI:SS')";
allocate auxiliary channel ch1 type disk;
duplicate target database to testdb;
}
exit