6 per day.. yup those are a daily resource.. and they are the only limit on those spells the healing surge has more limits than them. Unless you now figure they are at-will spells.... which just happen to require a daily resource.
4e PHB Page 15, thumbnail titled: Attack Powers and Utility Powers.
... Daily Powers are so dramatic and powerful that you can use each only once per day.
4E PHB Page 54
A daily power can be used once a day.
So a second wind, that can be used more than once a day is... Regardless of the tied resource, second wind can't be a daily. But loving your enthusiasm.
Also, I said second wind in the new system should be optional and no more than a daily.
You said that's how it works in 4e, and that is incorrect.
But, enthusiasm.