I did DXB-SYD-AKL on 26/27 May. Sector from SYD to AKL had only myself in F! So the FA alloted me 30 minutes of water for the shower!
Even with the normal 5 minutes allocated to me on the DXB-SYD sector, it was more than enough to completely refresh me. The shower on the A380 is a lot better than many showers in so called 5 star hotels!