In the past anywhere from 7 days to 4 weeks.
Nowadays as Australia Post has gone to shit it takes a week to get anything within Australia, so I 'd be more at the 3-4week end of the spectrum.
Yeah. I agree. I live in Spain and it took around 4 weeks to get it to me.
I think on the bandcamp webpage there is a link to contact the band to ask anything if you have a problem.
https://skarletrock.bandcamp.com/album/sk-rlet