Fully agree with the importance of 'niner'.
Been hearing a few excessive readbacks lately (p'raps known to get a bit verbose myself, though I try not to) - the 'line up behind' one gets them.
I know ATC are supposed to say the word 'behind' twice, but there's a bit of readback creep sometimes and it gets read back twice as well.
I'd go back to saying the callsign first any day, not necessary to change it, I thought, and it just feels unnatural (shows I'm getting older I s'pose).