The topic of practicing over breaks has come up several times in Horn Matters, with this article perhaps my most comprehensive on the topic. It is more directly addressed to summer breaks and horn students.
But what if you are not a student and the break is not a longer break? Such as over the holidays?
Lately I bet close to half of my actual practice has been from a classic old publication, the Schantl/Pottag Preparatory Melodies to Solo Work. The book is described further in this article.
What I like so much about this book is that the etudes are not long and they are very musical in nature.
Related to this, we just finished brass juries today at Arizona State and my number one comments to students had to do with focusing on making nice phrases and playing in tune. Music such as found in the Preparatory Melodies book is perfect for this as a focus.
As noted in the article linked earlier in this article, Pottag selected most but not all of the horn etudes from a longer collection of etudes by Schantl. The ones he did not include I put into a handy PDF (22 Melodic Etudes by Josef Schantl) that may be downloaded here:
UPDATE: That free PDF is no longer online, but I have included these as part of a new publication, described here.