Up to this time in Silas Marner, how long has Silas lived in Raveloe?
On Chapter 1, part 1, we are given a good description of Silas Marner, and this is also the part when we find out that he had been living in Raveloe for 15 years as of that point in the story. The passage reads:
It was fifteen years since Silas Marner had first come to Raveloe; he was then simply a pallid young man, with prominent short-sighted brown eyes,, whose appearance would have nothing strange for people of average culture and experience, but for the villagers near he had come to settle it had mysterious peculiarities which corresponded with the exceptional nature of his occupation, and his advent from an unknown region called "North'ard".
We know that Silas is representative of the advent of the new and the onset of ambition, therefore, his background helps create an air of mystery and foreshadowing about his character.