Such a danger of a life sentence exists no more. In United States v Haymond, the Tenth Circuit found that portion of the statute unconstitutional. As summarized by the majority:
We conclude that 18 U.S.C. § 3583(k) violates the Fifth and Sixth Amendments because (1) it strips the sentencing judge of discretion to impose punishment within the statutorily prescribed range, and (2) it imposes heightened punishment on sex offenders expressly based, not on their original crimes of conviction, but on new conduct for which they have not been convicted by a jury beyond a reasonable doubt and for which they may be separately charged, convicted, and punished.There is also an interesting discussion of sufficiency of evidence as related to evidence of thumbnails in a child pornography case. Although the Court did not reverse on this ground (remember the standard of proof in supervised release revocations is preponderance of the evidence) the discussion is worth your time.