Thanks Beefstu!

I went through all kinds of max time and still got the same issue.

I thought, rather than using unitl time, I could do the script in steps like this:
Although they are all DONE on the auxiliary host:
1. Do a backup archivelog all (of the target db arch logs)
2. Grep the max sequence# from rc_backup_archived_log_details
3. Print max sequence#+1 as the next_sequence (to be used in the duplicate unitl sequence ..... step)
4. drop auxiliary db
5. rm all files just in case they are lingering
6. startup w/ initaux.ora (only contains db_name)
7. run the duplicate command
8. set db to noarchivelog mode.

However, these are all done via code blocks in a shell scripts. I haven't figured out how to do a exception handler yet. Currently, I have a sleep 60 between each code block. Might not be a ideal way to script things.

I guess, the key point that I am not certain is, there is always many ways to skin a kitty, but is my way correct?