Geralt should be older and Sapkowski contradicted himself
The Kear Morhen massacre took place 50 years before Triss was born. Geralt is in his 50s in the books. The Trials must have been performed on him by specialists, because Vesemir, first of all, wasn’t knowledgeable about them—he was a swordsman—and second, even if he had some understanding, further specialized alterations were made to Geralt, which strongly implies experts being involved. Geralt was about 10 (a little over 10) years old during the Trials.
In other words, based on the information from Sapkowski’s books, Triss hadn’t been born yet, because about 40 years had passed since the Trials of the Herbs.
Honestly before The Crossroedes of Ravens came out everybody thought that Geralt is more then 80, but Sapkowski for no reason at all made a silly contradiction and made Geralt younger than he feels like to be.
EDIT: If Triss is in her fourties, than the massacre happened 90 years ago, which makes geralt a hundred in the books, which many people expected.