As long as its in my claim window I can claim it whenever after the anniversary? Even like a year from now? And if so can someone link the source? I don't wanna sit on it for the future and risk it disappearing once the anniversary ends.
I would say it is very safe under the claim screen but I doubt you will find a source that will guarantee this and even if you did they could change it the minute you look away from the computer screen. I have claims dating way back to the beginning and many more from when LON was taken down in 2016 and everyone gave away their LON goodies and this one Qeynos Shield of Foundation from 2008. In fact when LON was taken down they advised everyone that while the LON servers would die, the items, so long as they were put in your claims would stay until you claimed them. Just like the game cards, I have quite a few and they work fine every month.