The phrase "are only infrequently" is correct and usable in written English.
It can be used to describe something that happens rarely or not often.
Example: "The results of the experiment are only infrequently replicated in other studies."
Alternatives: "occur only rarely" or "happen infrequently".
The alkali earths are only infrequently used as supports despite the fact that they have many properties favoring their use.
But for stocks that are only infrequently traded, human intermediaries serve the valuable function of smoothing what would otherwise be erratic swings in price, for example by purchasing shares during periods when buyers are nowhere in sight.
It is possible that at least some of the apparent gaps in the species' range are more imagined than real given that all parrotlets of this genus are only infrequently seen, and then usually only in high-altitude flight, making their identification extremely difficult without robust knowledge of their flight-calls.
In this respect, it is also important to note that the RRMS patients, which are only infrequently treated with MTX (only as a second line treatment), do not show altered cfDNA levels.
Even though both the importance of aid agency security management (HPN 2010; Egeland et al. 2011; Collinson and Duffield 2013) and the relevance of technological progress in the aid sector (e.g., IFRC 2013; UNOCHA 2013) are studied on their own, security management and technological progress are only infrequently studied in junction.
Meyerbeer's works are only infrequently performed today.
In response, consumers conserved water and reduced demand; as a result, today the desalination plant is only infrequently operated at capacity.
Civilians in the defeated community were only infrequently taken prisoner, for as captives they were sometimes a burden upon the victor.
Its utility and safety during pregnancy is largely unknown because it is not often required and because its use has been only infrequently reported in the published literature.
Under Ms. Berger, Vertigo flourished with hardcover and paperback collections of its monthly comics series, at a time when DC was only infrequently anthologizing its mainstream superhero titles, and she became a magnet for younger talent.
