The phrase "several years" refers to an unspecified number of consecutive years. It can range from two or more years up to a decade or longer, but it is not precise and can vary depending on context.
We've used these buffalo plaid stockings for several years now for our five children. (whitearrowshome.com)
Chances are that any fixed rate mortgages that you signed up for several years ago have become significantly lower. (syndicatemortgages.com)
We have seen a continuing shift over the past several years of elected officials working for the benefit of corporations and special interests, and away from helping the people of our great state. (advocatesaz.org)