How many of each Legendary are you keeping?

6 per each.
I just powering up Mewtwo, I think he is the only usefull legendary pokemon.

I'll keep my one and only Lugia no matter what.

Haven't transferred any of them yet, figure they could be valuable trade bait if that ever happens. If it doesn't I have a lot of Mr. Mimes I'll need to transfer before I worry about my legendaries.

88.9+ iv or transfer

All the wonders. None of the impressive.

I'll probably transfer them during double candies...At the end of the day, after you get 1 at least, the rest are extra so I'll probably keep 3 tops and leave it at that...

I save nothing for trading since there are plenty of other people already doing that and most people won't trade you anything worthwhile for a crap IV mon neither...(or at least anyone who needs a legendary bird would have anything you really need...)....

I'm keeping all of them for now. If they become available again then I'll consider transferring some if I need the bag space.

But until they're rereleased, I would rather keep them as one Pokemon storage space is far less valuable than something that might not be available again.

Keeping them all even until the next Double Candy event or Trading, whichever comes first. Only keeping 1 cause it was my only one that was at least a 91% out of all of them which happens to be a Lugia. May keep all my Zapdos too til they come back just because I managed to get a 100% catch rate on him too. 11/11 Don't want to ruin the chain so far I have with him and get some bad luck for transferring some.

I don't have any of the legendaries yet, but I wouldn't want to get my first of any of them via trading. It's excitement or bust for me. First legendaries by trading sounds like a big yawn. (I'd be interested to hear if others without legendaries disagree, and would be content to get them through trading.)

Higher-IV or powered-up legendaries seem like they could have some future trade value though for sure.