In the following exchange, "you may well ask" is used after a question has been asked.
‘What’s all the noise?’ ‘You may well ask.’
But I'm wondering whether "may well V" is normally used after the action denoted by V is completed or the above sentence should be treated as a fixed expression.
It seems correct to say "You may well do this or that" when giving advice. The action denoted by "do this or that" has not yet been completed.