for the long haul

For a long period of time; permanently or for as long as something takes to accomplish, attain, etc. Usually refers to one's commitment to someone or something. Jill knows that obtaining a PhD is going to be tough, but she said she's in it for the long haul. Once we sign this agreement, we'll be committed to this project for the long haul. I love you, and I'm not going anywhere. I'm in this for the long haul.