Do not boil the sugar in the water together. It changes it and it's not good for them. And if you store it it won't be good for more than a week. Please don't take my word for it, do some research. I belong to a hummingbird website so we get all this information daily.
No, you shouldn't be boiling the water with the sugar in it. And it doesn't store very long. I know you've been doing it for years but I've been long to some websites that talked about this daily. Don't take my word for it do some research.