You can start building up the 13 weeks after 156 benefit are claimed, so, yes, it applies after 312 days benifit too.
A 3 hour round trip would not be valid reason in my opinion as it may be only 5 miles drive either way in traffic! Seruiously, though, it would be wrong to try and tell you what is a valid reason for leaving employment as many factors taken into account by individual deciding officers: wages paid fro work doen, distance from job, suitability of job, attitude of employer/employee, state of health, affect of job on health ...the list is endless. The best rule of thumb is your own honesty: the rule of disqualification is there to prevent people claiming welfare instead of holding down a job. The deciding officer has to determine this from the application submitted, plus they will get the employer's view of why you left as well.