In the sentence,
the phrase "as long as" reinforces the "may" to indicate the optional nature of the Limit. If it were not supposed to be an option, the sentence could read,
This optional nature of Limits during your turn felt wrong to me at first. But the more I looked at the phrasing on the cards, the more I was convinced that that was the intention. (Andy's YouTube video helped a lot too.) It's possible that earlier editions had different phrasing, and a different intention, but I'm now convinced that optional Limits during turns is the intention for Fluxx 3.1.
Of course, in our own games we can make house rules to play the way that feels best to us.