It depends.
Many people with bad posture can fix it by simply being mindful about it and reminding themselves to stand more erect. Doing things like stretch/yoga can assist with this as it helps keep your muscles loose and be more accepting to your alignment changes.
If you are experiencing pain, or if you have something like scoliosis causing your bad posture a chiropractor may be of assistance.
When you start to see a chiropractor you do typically need to make a few frequent visits to get things moving back to where they belong. Then the time between visits lengthens, depending on various factors. Some people continuing going for continual maintenance due to things like prolonged problems and issues that happen because of what they do day to day. Others find they are able to stop at a point.
If your bad posture is not do to a severe spine curvature, you could go see one for awhile to speed along you improving your posture. Once it was better there would be no reason you would have to keep going unless you want to. Typically most people keep going to a chiropractor is because they want to, because they find benefit in it, but they don't have to.
I go once a month for general maintenance. Sometimes I can go longer other times I can use more...usually because I did something to muck up my back lol But if I didn't go at all I'd probably be limping and living on pain killers.
Whether you go see one is totally up to you.
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