100% agreeing with NotFuzzyWarm on this one... Testnet isn't created to be secure, or a store of value... It is created to test.
And if you use it for the purpose it was created (testing), it does a good job.
Use testnet to test out new wallets, new scripts, spend, receive, create paper wallets, create an airgapped setup, test out the payment gateway on your new service
, test out my new bitcoin core v29.
0 docker image
. Afterwards, either keep the tBTC or give it away, as soon as your tests are done, there's no real use for the tBTC anymore.
Hey, if you ever want to test how a 51% attack would work, testnet would probably be the chain you'd use to do so 
Do realise that having zero value does not mean it's free to mine the tBTC...
I'm always a bit grumpy when i see company's throwing relatively modern ASIC's towards tBTC mining. I always wonder why... In my mind, tBTC should be something that it basically thrown your way whenever you need it (be it faucets, or just cpu mining). Throwing "good" ASIC's towards tBTC mining makes it rare. I know i used to ask for collateral whenever i loaned out tBTC v3 in the past, because it was allmost impossible to mine any in meaningfull quantity's, and nobody was giving away meaningfull quantity's on faucets either so i asked for collateral so i'd get most of the tBTC back for the next person that needed some.