project reporting for directs where other items are higher priorities

I've listened to the podcast about assigning reporting and deadlines with the tasks for projects (big and small). We have what I think is not a unique situation and I'd like to poll others about how they handle this situation with their employees.

As the Team Lead, the set of contract employees that I work with are primarily responsible for supporting end users and internal client teams. This work comes in sporadically and is usually higher priority than other tasks that we assign internally to the team. We have weekly one on ones as well as daily scrum calls to discuss general tasks.

Generally, I would have the team report on the status of projects during O3s or the daily call. Being a "typical" lead/manager these days, I don't tend to force them to assign dates to the completion of their projects. I'd like to change that behavior on my part. At the same time, I want to make sure that I'm flexible with the deadlines that we put down on these internal projects. Typically, they are documentation, user validation, or similar tasks.

Is it ok to have "floating" deadlines on these types of projects? Is it ok to keep moving those deadlines out almost continuously? At what point in everyone's experience does a task that has been moved out by a month or more have to become the priority task and actually get completed? How do y'all handle this type of situation?

Thanks in advance for your input!!!

- Scott M.