Sometimes it just takes longer for some people. My mom smoked her nightly cig for at least 3 months into vaping. I still cant believe she succeeded in quitting. Give your dad more time and continue your support. I'm betting he may have smoked much much longer than you and it's a die hard habit. On a side note, when my Sis was preg she had a hard time the first month and was still smoking 5 a week. Her DR told her not to repeat this BUT She said 1 or 2 a day isn't as bad as some think. Not good but shouldn't cause any real damage to a person. Good luck to you and your family!