Fifth Circuit apparently taken over by aliens, issues restraint on prosecutors "vouching" for law enforcement

At Deliberations, Anne identifies a beauty of a Fifth Circuit opinion in a Texas case laying down the law regarding what prosecutors can say in closing statements to bolster the credibility of police testimony. She writes:

Here's the line you're trying to draw: it's okay in closing argument to suggest what inferences jurors should make from the evidence, but it's not okay to insert your own credibility by vouching for the credibility of a witness. The classic example of vouching is when the prosecutor says, "I've known this FBI agent for years, and I can tell you he wouldn't lie."

Got it? Okay. In the the trial that led to Fifth Circuit's United States v. Gracia opinion yesterday, defense counsel argued that the federal agents were lying. The prosecutor responded with the following arguments. Which ones are permissible inferences from the evidence, and which are impermissible vouching? Here you go:

1. "First, the prosecutor expressed his opinion to the jury that the agents were 'very, very credible' witnesses ('Statement One').
2. "Second, the prosecutor asked the jurors rhetorically whether they thought that an agent 'who has worked as a law enforcement agent for many years, that is his career, that is his chosen life, a man from this area, a man with a family, do you think that he would throw all that away by taking this stand and taking an oath and lying to you to get Mr. Gracia'; and whether the agents 'would put their careers and criminal prosecution on the line for committing the offense of aggravated perjury' ('Statement Two').
3. "Third, the prosecutor told the jury: 'I’m going to ask you to respect their efforts as law enforcement officials and to believe the testimony that they offered' ('Statement Three').
4. "Fourth, the prosecutor admonished the jurors that, to acquit Gracia, they would have to believe that the agents 'got out of bed' on the day they arrested Gracia and decided that this was 'the day that [they] were going to start [a] conspiracy to wrongfully convict Mr. Gracia' ('Statement Four')."

I think most Fifth Circuit watchers will be shocked to learn, as Anne was, that the court's answer was "all four" statements amounted to vouching, and indeed constituted "reversible plain error," overturning the conviction! I quickly rushed over to the Texas District and County Attorney user forums, assuming they'd already be in a tizzy over the opinion, but apparently word hasn't filtered down to the front lines.

From readers with courtroom experience, how often do you hear prosecutors make statements similar to one or more of these four in closing arguments? They're certainly common enough in the political and rhetorical arena. Via Capital Defense Weekly.