Just look at the list of main characters and think about how many years it will take just to get them made!!
Frodo, Sam, Merry, Pippin, Aragorn, Boromir, Gandalf, Legolas, Gimli, Bilbo, Elrond, Arwen, Galadriel, Saruman, Wormtongue, Theoden, Eomer, Eowyn, Faramir, Denethor, Gollum, Ringwraith, Witch King
That doesn't include others like Haldir, Celeborn, Elendil, King of the Dead, Mouth of Sauron, variations (white vs. grey Gandalf), Easterling, prologue elf, various orcs, etc. (They might also attempt something huge and expensive like a Sauron, Treebeard, Cave Troll, or Balrog.) If they produce 3-5 a year, it could take the better part of a decade before we're all satisfied...