Almost all the event currencies are removed shortly after the events, not just the TH oddments.
I still have 144 spare Charity Tokens left from the Mental Health event that can't be converted to anything.
I don't doubt all these events will be recurring, no reason to think they are not. However, it is nice to be able to convert the event currencies to something, perhaps a tiny bit of xp after the events though.
Yeah, well, I'd like to be able to have the option to turn oddments OFF. Other event currencies, like the charity event tokens, are separate from the th stuff, but these blasted things u get stupid oddments in place of coins if you want to cash something out. I looked at the store. Nothing I want to buy of the few things I CAN buy. I have more of the chromatic and metallic dragon tokens banked than I will ever use so I don't need more of those, as far as what's left, I don't want tight springs because I never use spring cleaner (and tight springs are untradeable ofc), silverhawk down I might get, but sheesh. And a th key is 550 oddments? that means I'd have to cash out the items from 30+ TH keys to get enough oddments to buy 1 more key. The odds are ridiculous. Everything on the 2nd-4th tabs I already own so why bother.