I use a slightly different approach which I find works very well.
For me this is THE recommended way.
I sync the DCIM folder etc. from the phone read/write.
The synced folder on the PC is part of the Shotwell library folder (~/Pictures).
I can then delete photos both on the phone and PC, which I find convenient.
It avoids filling up my nightly backup with “junk photos” if I tidy up the same day.
Then I have a script which picks everything older than 90 days from the synced folders, and moves them to another folder under Pictures on a yyyy/mm pattern, with the effect of deleting them from the phone, but Shotwell detects the move “transparently”. This way I have almost instant backup from my phone and access from the PC, but keep the memory use on the phone under control.
(There is an article online somewhere describing this approach which I can’t find right now.)
I’ve been working towards making my little Python script fit for publication, as it handles exif dates and name conflicts better than I’ve seen elsewhere and adds some other niceties, but I’m happy to send it to anyone here “as is”, if you are interested.