In my experience I wake up within the first 30 seconds about 1/4 of the time
last 30 seconds to a few minutes 1/4 of the time
last several min to like 5 min 1/4 of the time
and last quite a while some of the time like up to 15+ min at most

take in your surroundings a bit, then having a goal and keeping moving can help keep you in the dream (even if its a goal you make up in the dream it will still help)