Overview
It’s true that Thulecite, as great as it is will someday run out. But there is a method to have infinite Thulecite though it is costly and should not be attempted until later game.
How it’s done
You will need (atleast) 3 Green Gems, 20 Thulecite, 2 Living Logs and 7 Nightmare fuel. (I also reccomend you bring Sanity restoring items and lots of them, jerky works good) You will also need to be in the ruins as you’re going to need a Pseudoscience Station. Start off by crafting a Construction Amulet and Deconstruction staff. Now equip the Construction Amulet and make 5 Thulecite suits which will now only cost 15 Thulecite in total. Lay them on the ground and use your Deconstruction Staff on them to get 30 Thulecite back for a profit of 15 Thulecite. Now this method is pretty easy except for 1 thing, and that’s getting the Green Gems. Green Gems can be found by destroying ancient statues that have a Green Gem on them or very rarely ( 0.02% chance) from Tumbleweeds, this means Green Gems are rare. But there you go Thulecite is infinite.