Until you finally opt out (2,2)
I believe the answer is:
up to
'until' is the definition.
(I've seen this before)
'you finally opt out' is the wordplay.
'finally' suggests the final letters.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
The final letter of 'you' is 'u'.
'opt' with letters rearranged gives 'pto'.
'u'+'pto'='UP TO'
(Other definitions for up to that I've seen before include "Plotting" , "Capable of" , "As far as a certain point" , "As far as or as many as" , "Engaged in doing" .)