UPDATED: OCT 2022
= duration or period of time
= 5 days, 2 weeks, many months, several years, most of my life, a long time.)
= usually used with a number (for 10 days, for 2 years)
You can use with All tenses.
Usually answers the question “How long”.
= a specific time in the past (last week, last month, last year, March, 1999)
You can’t use with simple present tense.
“I work with her for a long time.” <= incorrect
You must use Present Prefect or Prefect Continuous