The phrase "are constantly varying" is correct and usable in written English.
It can be used to describe something that is in a state of continuous change or fluctuation.
Example: "The weather patterns in this region are constantly varying, making it difficult to predict the forecast."
Alternatives: "are always changing" or "are in constant flux."
To meet their needs, we are constantly varying and expanding our selection of traditional and ethnic foods".
This was able to happen because traffic routes are constantly varying, with ISPs making frequent 'announcements' of changes using the Border Gateway Protocol (BGP).
Whenever the conditions are constantly varying, coffee may seem to deteriorate rapidly.
The arrangement of these excerpts was constantly varying according to the individual compiler's concept of the hierarchies of human knowledge; some of these classification systems were more suitable than others, but none was completely successful in meeting the tastes of the reading public, because there was no general agreement on the essential order of ideas.
This illustrates the fact that the high-latitude geomagnetic field is constantly varying and the rate of change of the field rarely vanishes.
The design of scheduling algorithms in WiMAX networks is specially challenging because the wireless communication channel is constantly varying.
Real mobile phone emissions are constantly and unpredictably varying and thus are very different from simulated emissions which employ fixed parameters and no variability.
In large urban settings, children are constantly exposed to varying amounts of assorted toxic chemicals both inside and outside the home.
A constant carrier RF wave modulated by a constant ELF field can certainly be simulated but this is not the case in real mobile telephony signals, in which both the carrier and the modulation are constantly and unpredictably varying in intensity, frequency, and waveform during a phone-conversation [ 7, 28– 30].
