Profiles remain active in the pool for 12 months. After 12 months you may re-submit a new profile if you remain eligible.
You do not need a job offer to enter the Express Entry pool, but a valid offer supported by an LMIA generally adds significant CRS points.
All required language tests (IELTS General, CELPIP-General, TEF/TCF Canada) must be valid (taken within the last two years) at the time of profile submission and application.