the 22hr playback is under ideal conditions where you do not take any call, with minimal use of display. To be precise, if you use the phone as mp3 player, the battery will last for 22hr. But the more you use it as phone, the lower the battery life will be. Surely, this is a good phone and directly competes with N73.
I went with my friend to Mobile Store to get a music phone. The demo piece's slider (for 5610) lost is spring action. So, you better take a note at this and search more forums about the slider's life. one who uses it for about a month will definitely say it's good but you need to check with someone who used the phone for somewhere around 4-5 months (don't know if the phone's available for past 6 months).
For peace of mind, I vote for N73me and K810i over N5610
K810 has superb battery life, stylish design, awesome camera and very good music quality.