If the string is supposed to say "indefinitely" only, it shouldn't be a variable (or at least translators should be made aware in the string comment). If the string is covering date and time, "until" should be added.

Such strings should normally substitute {until} with either "indefinitely" or "until Jan 3". This way "until" is present when necessary. Isn't this the case?

The screenshot made me question this one. I believe a string description could prove helpful in this case, explaining how the {until} token works 😊