The phrase "countless trials" is correct and usable in written English.
You could use it to describe a long and persistent effort to achieve something, for example: "Throughout his career, the scientist endured countless trials and tribulations in pursuit of a breakthrough."
The two groups have survived countless trials.
It also seemed to herald the beginning of nearly two decades in which this onetime economic superpower has suffered countless trials, including last year's tsunami and nuclear accident.
Countless trials are under way to assess technology that can monitor people who have been diagnosed with heart conditions, or diseases like diabetes, from the comfort of their own homes.
As long as pharmaceutical companies design and finance more than half of this research; ghost-write many of the research publications; run countless trials but publish only those findings they wish without providing open access to their data; and are permitted to make scientifically unsubstantiated advertising claims, a true informed-consent for psychotropic medications will be unobtainable.
It took us a number of years, and countless trials and errors along the way, but we're seeing the beginnings of that vision realized.
Bouley is constantly learning and improving his food through countless trials in the kitchen, and keeping a close eye on the patrons in his restaurants.
BEATRICE INN After countless trial dinners and private parties, Graydon Carter's third restaurant has opened, with a bar, a nicely upholstered library-style dining room and an airier rear room.
The merits of natural suckling have been evidenced in countless clinical trials.
Someone somewhere is going to prove to be allergic to a vaccine, or will react in a way that runs contrary to everything scientists anticipated after subjecting it to countless clinical trials.
While the benefits of breastfeeding in protecting infants from infection and diseases have been shown in countless clinical trials, there are still many instances when formula milk may often be safer or help to resolve nutrient deficiencies.
This departure stage is followed by an "initiation," during which time the hero confronts countless tests, trials, allies, enemies, temptations, failures, and triumphs.
