Detect Spell-like ability at will

[Mr Funtastic]

When a class provides a detect spell-like ability (such as the paladin's detect evil and the warlock's detect magic abilities) how exactly is it activated? I do know that it's a standard action to activate them (since they are spell-like abilities) but which one of the following is true?

1. Is it active at all times?
or
2. Is it activated any number of times per day and remains active as long as the character concentrates up to the maximum that is stated in the appropriate spell's description?
or
3. Is it activated any number of times per day and remains active as long as the character concentrates (no maximum duration)?

Me and the gorillas that I have for friends, have been using it as stated in (1), but I gave it a second thought and now I believe that (3) is the way it's meant to be played.

 

[hong]

As per the spell. Activated any number of times per day, and remains active as long as the character concentrates, up to a maximum duration. For detect magic that's 1 min/level, and for detect evil it's 10 min/level.

 

[Mr Funtastic]

I see.
It does make much more sense that way, though it does seem a bit silly imo for the ability to have a maximum duration since it can be activated and re-activated at will.

 

[Ogrork the Mighty]

Which shouldn't be a problem unless a battle lasts longer than the duration of the spell. It's pretty rare indeed for a battle to go longer than the 1 min/level spell duration.

 

[Legildur]

Which shouldn't be a problem unless a battle lasts longer than the duration of the spell. It's pretty rare indeed for a battle to go longer than the 1 min/level spell duration.

Or for someone to concentrate for that long on a non-offensive spell during a combat.