We tried. His assistant said
he was on SABBATICAL.
The Big Bang Theory Season 5, Episode 17
And he was able
to take a SABBATICAL from...
The Big Bang Theory Season 7, Episode 24
I'm taking a SABBATICAL because
I won't kowtow to mediocre minds.
The Big Bang Theory Season 1, Episode 4
a temporary SABBATICAL
The Big Bang Theory Season 12, Episode 5