What you are wanting to do doesn't work with the word onus because the onus doesn't go away.
Consider "the onus of caring for the elderly usually falls on their children".
It doesn't matter if Wednesday is your day in the barrel, the onus doesn't get discharged likevanquished in the way a burdento-do list entry does. At least we don't talk about it in that manner. An onus is durable. It lasts as long as the actual circumstance does, regardless of how many actors enter and exit the stage. You don't talk of having the onus to do an oil change.
The idea of discharging an onus is nearly always cast in the negative or the very unlikely.
Some usage examples-
The purchase of guaranteed railways owned by foreign companies likewise added largely to the bonded indebtedness, though the onus was in existence in another form.
..
If so, apologetics is literally a science, and it is pedantry to claim the defensive and pretend to throw the onus probandi upon objectors.
Read more at http://sentence.yourdictionary.com/onus#D366q73Z7a0D2BBH.99
The onus is on my generation to remember the previous chapters in Anglo-Jewry's story.