How many Lugia raids are enough?
Given the small usefulness of Lugia in the game how many of them are you going after? I expect I will do the one free raid a day for him in hopes of Rare Candy but it seems like multiples of these are the most likely to visit the professor. If I am looking this wrong where or why should I keep an army of them?
Personally, I think Lugia is one of the best mons in the game. His relatively low CP makes people underrate him, but he has great STAB moves to go along with his huge bulk.
As others have said, I'll do 1-2 per day for the rare candy, Lugia candy, and chance at a shiny, and when Lugia is gone again, I'll TM my best (or shiny) one to ES/SA, and power it up to go alongside my already powered ES/FS version.
I've got enough Lugia's - including a Shiny. I've got a 96 and a 93, to go with my old 87 that I've powered up (thinking it was going to be the best Lugia I would ever get... argh. What a waste of Rare Candies!!). My daughter has a Shiny and a Regular Lugia.
Once my wife has her Shiny Lugia, I'm out of the Lugia raids.