Doctor said wear permanent splint, even after6months of an arthroscopy. also fills of crowns wont last, so wear splint not to affect the joint, is ok?

Yes wear the splint: You should wear the splint for the rest of your life, if you have no more discomfort, the splint should protect the joint and relief the pressure. If you have problems after the surgery it will help protect the joints. Please rephrase the second part of your question.

Hard to say: This is en example of a difficult question to answer over the internet. Sometimes a splint is a diagnostic tool that points to a more definitive long term solution and sometimes it is used long term. I don't understand the last part of your question, either but ask this of your treating dentist and if you don't get a clear understanding of the rationale for long term wear, seek a second opinion.

Splint wear ?: The question is not clear to me but the need to wear a splint forever is not a good option for most. We finish our cases with orthodontics or crowns after splint wear and pain relief. Some wear nightguards after reconstruction or orthodontics to correct a bite issue.

Simple solution: See an OFP doctor to receive the scientifically validated and best medical-based treatment. The proper diagnosis is the key to successful treatment. They are the expert in this field.

Follow instructions: You should try and follow all post-op instructions and ask about prevention of further issues. You want to avoid another surgery, if possible.

Depends: Depends on what your oral surgeon tells you. Is your splint being managed by a TMJ expert? If so, follow his advice long term.