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Another question highlighted this Space X commentary for the GRACE-FO launch:

Now in order to fly an efficient trajectory for both of the payloads, we’re actually now running the second stage engine at lower power. That means the burn will be longer. For folks who used to seeing us shut down the upper stage engine nine to nine and a half minutes in to flight, today we’ll actually be shutting down the engine just past T+10 minutes into flight. As planned for today, the longer burn at lower power obviously takes more time, but gives us a more efficient trajectory.

The GRACE-FO orbit is comparatively low and circular. Entering it in the usual way, with a boost followed by a wait then a second circularization burn, would have put those two burns about 2 minutes apart. Instead, Space X used a longer single burn.

It could be that Space X wanted to avoid a "hot" restart of the engine. They routinely restart after the engine has had 20+ minutes to return to lower temperature. Has any mission had a restart after a shorter interval?

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    $\begingroup$ Didn't they do multiple restarts with the Falcon Heavy launch? $\endgroup$ – GdD May 29 '18 at 10:23
  • $\begingroup$ @GdD FH Demo has about 20 minutes between the first SECO and the restart, at the low end of the "pretty typical" range. spaceflight101.com/falcon-heavy-demo/flight-profile $\endgroup$ – Bob Jacobsen May 29 '18 at 14:28
  • $\begingroup$ is hot restart your own term? I haven't found references to specific issues, but maybe I'm looking in the wrong places. $\endgroup$ – GdD May 29 '18 at 15:18
  • $\begingroup$ I'm not sure "hot restart" is an official term, but it's pretty common when discussing smaller engines, i.e. dtic.mil/dtic/tr/fulltext/u2/a261774.pdf and more recently researchgate.net/publication/… $\endgroup$ – Bob Jacobsen May 29 '18 at 15:41

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