Using removable HDD as target?

I want to do:
- SSD will do hourly snap, even when the target HDD is offline
- daily snaps will be send over to HDD when it is online (let's say, the HDD will online once every 7 day)

Is my below conf file OK for that?

cat /etc/btrbk/snap.conf
`
timestamp_format long
stream_buffer 512m
snapshot_preserve_min latest
snapshot_preserve 24h 7d 4w

target_preserve_min no
target_preserve 0h 21d 10w *m *y

volume /var/vols/250G
snapshot_dir _btrbk_snap
target send-receive /var/vols/8T/_btrbk_backup/250G
subvolume 850evohome
subvolume 850evoroot
subvolume var_log
`

Start by reading the configuration in /etc/btrbk/snap.conf and the btrbk documentation for snapshot and send-receive targets. Verify whether the shown settings support hourly local snapshots while the removable HDD is offline and daily transfers when it is online; document the result and any required configuration changes.

Written by the indexing model from the issue text.