In response to pilots being told during their interview about quick upgrades (1.5 yrs), I had a different experience. I just interviewed a few weeks ago, and was told that moving from the 320 to the 330/340 would be about 1.5 yrs, and that an upgrade (captain position) to the 320 would be around 4 yrs. The captains conducting the interview were also sure to point out that this IS the airline industry, and that things could change... they made it clear that those time lines could very easily change, and not to take it as set in stone.
I'm from the US, so my definition of an "upgrade" is a Captain, or PIC position, not moving to a shinier jet, so I may have misinterpreted the original post.