Ring of sustenance on an elf/whirlwind attack question

[Avaris]

A ring of sustenance provides refreshment to the mind and body, such that instead of 8 hours sleep you only need 2. My question is, how does it affect elves given that they don't actually sleep?

I see two possibilities... 1) it doesn't (which is dull) or 2) it reduces the trance time needed as well by the same proportion, so to 1 hour a day, or even eliminates the need altogether. I'm going to run my ideas past my gm anyway, but I'm interested to hear other viewpoints on how this should work.

Edit: got another question re: whirlwind attack, see below

[The Boz]

1 hour/day trance seems fair.
One question: Does it only need to be on while you rest, or do you need to wear it for the entire day?

[Avaris]

You need to wear it for a full week before it takes effect. No passing it around the party!

Edit: a further question for anyone who happens across this thread: Can the whirlwind attack feat be used while wearing heavy armour? Some of the pre-reqs can't, but I'm unsure on the feat itself...

[Cog]

Elves gain no benefit from eight hours of sleep, so that part of the ring's ability doesn't do much for them.

Whirlwind Attack doesn't require the use of any of its prerequisite feats, so it works in heavy armor.

[Thurbane]

I'm going to post my usual Whirlwind Attack advice: you can get it without all of the messy prereqs with a 3 or 4 level dip into Binder and the Improved Binding feat (4 levels of Binder get's you a bonus feat, to use on IB). Binding Paimon, you get Whilrwind Attack, plus a mess of other goodies, including Dance of Death (get an attack on every opponent you threaten as you take one base movement, usuable 1/5 rounds), Uncanny Dodge, and an untyped +4 bonus to Dex.