The best resource of all of your DS-160 questions is the USDOS web site.
Validity is usualy as long as the information in the application is current and it can be used only once.
The web site also have a series of q and a's on the DS-160 processing.
Legal disclaimer: The statement above is provided by CC Abbott is based on general assistance and not intended to be a legal opinion because not all the facts are provided. The person requesting information and all others reading the answer should retain an attorney who is permitted by the state bar within the jurisdiction who can examine the complete facts and provide a legal opinion on your case. All information provided in the above answer and other information provided by CC Abbott does not create an attorney/client relationship within any state of Federal law.
The answers provided are detailed enough.
LEGAL DISCLAIMER: The answer(s) given are only to be deemed general in nature as all of the facts of your case were not provided and thoroughly reviewed. Any answers are NOT to be deemed as attorney advice as a full legal opinion can NOT be provided at this time without a complete analysis of all of the facts regarding your particular matter. Any and all statements provided do NOT in any way create any type of attorney/client relationship.
No expiration on the completed form DS-160 unless there are changes made or the photo is out of spec.
713-772-2300. All information provided is general in nature. Please consult with an immigration attorney with full details of the case.