Permanent Harvesting Sickle

So I recently bought the Clockwork mining pick and was looking forward to getting a permanent harvesting sickle but this... this Thresher-Sickle 5000 is strange. Yes, it's funny and reminds me of Bombur's dwarf-in-barrel-armor combat scene in The Hobbit but I can see it getting old fast.

Is there always a permanent tool in the store on rotation pick > sickle > axe? How often does it change? I'm wondering if I should just get it and try to ignore it or wait and see what the next one is.

Thanks!

Not always, we waited 3-4 weeks after the Molten Alliance Mining Pick was taken off the store, and the Consortium Harvesting Sickle was datamined, before they actual let us buy it.