How long are replays kept? Many are gone?

I noticed many replay fail to download.
For example the battles linked in old tourney threads like here:
http://zero-k.info/Forum/Thread/19927?postID=141148#141148
Are replays deleted after some time? (4,5 months?)

There were the various replay issues on github and and more that did not make it to tracker. But I think that was all longer ago.

I have been unable to find any downloadable replay that is older than 4,5 months.
For example go to replays-tab and search for a popular map that gets played all the time. Titantuel or Icyrun or so.
http://zero-k.info/Battles?Title=&Map=Icy+Run+v2&User1=&User2=&User3=&PlayersFrom=&PlayersTo=&Age=0&Mission=0&Bots=0
Look which replays work.

Some replays I am also fairly certain that I have watched them in the past, but now they do not work anymore. No idea how to confirm that.
Those replays are not downloadable but you recorded videos:
B386132 2 on Living Lands v2.03
B386051 2 on Iceland_v1
B387929 2 on Rapids_v1
..
Did you get the files from players?