I'll be using this time to just rest

[Maybo]

He asked for his fans to be patient, and said of his forthcoming shows that he is "physically, obviously, not capable of doing them".
He also smiled and blinked, showing his 240 million followers how the right side of his face did not move.
"This is pretty serious, as you can see. I wish this wasn't the case, but, obviously, my body's telling me I've got to slow down," he said. "I hope you guys understand. I'll be using this time to just rest and relax and get back to a hundred percent so that I can do what I was born to do." (Justin Bieber reveals facial paralysis after shows cancelled by BBC)

I have a question about tenses. Why did Justin say "I'll be using" but not "I'll use"?

 

[5jj]

He was probably thinking of the limited duration of this.

 

[5jj]

He was probably thinking of the limited duration of this.

See also the paragraphs below from this arttcle:

5. The modal will + be + -ing form

Progressive forms usually refer to a situation that began before a time point continues through and after that time point, and into the future, and is of limited duration. The combination of this idea with the modal will, expressing certainty, leads to the modal will + be + -ing form referring to a situation beginning before a future time point and continuing through that time point:

Sally’s plane takes off from Heathrow at 9 o’clock tomorrow, so by about midday she will be flying over Istanbul.

It is also possible that the speaker is more concerned with the pure certainty of the action happening than with volitional aspect that might be implied by the use of WILL by itself:

Emma will be seeing Luke tomorrow.

Some writers claim, with some justification, that this use of modal will + a progressive implies, by its lack of reference to intention, volition or arrangement, a 'casual' future. Depending on the context and co-text, the speaker may be intending a ‘casual’ futurity, or may be indicating a situation in progress at a particular time.