SELECT
  CASE
    WHEN lt_week = 0 THEN 'A. < 1 week'
    WHEN lt_week = 1 THEN 'B. 1 week'
    WHEN lt_week <= 4 THEN 'C. < 1 month'
    WHEN lt_week > 4 AND lt_week <= 8 THEN 'D. 1-2 months'
    WHEN lt_week > 8 AND lt_week <= 16 THEN 'E. 2-4 months'
    WHEN lt_week > 16 AND lt_week <= 32 THEN 'F. 4-8 months'
    WHEN lt_week > 32 AND lt_week <= 52 THEN 'G. 8-12 months'
    WHEN lt_week > 52 AND lt_week <= 104 THEN 'H. 1-2 years'
    ELSE 'I. > 2 years'
  END AS user_group
FROM your_table_name