When describing my tenure, I usually use "so far" to highlight my long time and deep experience in this company or institution. For example, "I have been doing XX since XXXX" or "I have been doing XX in XX company or institution since XXXX, and it has been three years now".

This expression can make it easier for the audience to understand your work experience and qualifications, and it can also make your experience more convincing and credible. At the same time, using "so far" can also avoid using too vague expressions, such as "a few years ago" and "last year", which makes it easier for the audience to remember your term of office.