Are you talking about bouncing up and down or "remaining sagged"?

For the first one, oftentimes upon (hard) touchdowns, there is some bouncing.

For the second one, the wings remain "sagged" while producing lift.
If there is still noticeable airspeed, the wing will still be producing lift, so there will be some "sagging" indeed.
BUT as soon as the spoilers are activated, (most) lift gets spoilt and the wings stop flexing.

It's actually very cool to see how the wings drop as soon as the spoilers are deployed

Are you talking about bouncing up and down or "remaining sagged"?

For the first one, oftentimes upon (hard) touchdowns, there is some bouncing.

For the second one, the wings remain "sagged" while producing lift.
If there is still noticeable airspeed, the wing will still be producing lift, so there will be some "sagging" indeed.
BUT as soon as the spoilers are activated, (most) lift gets spoiled and the wings stop flexing.

It's actually very cool to see how the wings drop as soon as the spoilers are deployed.