I must say I am a bit confused by this issue.

Are we really sure NFC reader is always active because if thats the case it could be done alot better by turn on/off X times sec. To save battery. Ofcourse fully turn off will save even more but then whats the points with tags on OTH.

No point poll constanly. I don't know how it implemented on N9 but its probadly turns on/off x times per second and not constanly on. I have it enabled on N9 all the time.

And about OTH. Wasn't there a lightsensor or similar that check if cover has connected?

I mean most logical if other sensor exist would be:

turn on NFC only when sensor is triggered make it on until NFC has been read OR timeout after a 1 second?

Or else implement it as most other readers. (Turn on/off X times sec) probadly 2-4 times per second should be enought (and active for 100msec this intervals) Thats what I remember from a reader I worked with on my old job...