Hi there and thank you for your question,
Typically a visa will be issued to you with certain restrictions applying. For example, even though you were granted a 10 year visa to the US, you may only be allowed to visit the US for 6 months at a time.
You would therefore need to visit for 6 months, then leave, then return again for 6 months, then leave again.
You can however normally obtain extensions to these restrictions, so that you could visit for up to 1 year without having to leave between. This will need to be done through the US consulate, and as long as you have good reasons for the required extension (e.g. touring holiday), it should normally be granted.
Have a look at this website for some more informaiton: http://www.workpermit.com/us/employer_b1_b2.htm
This also obviously depends on what visa you actually have, as some are more restrictive than others.
See this quote from the website: "Those entering on visitor visas will generally be granted 6 months admission (the maximum allowable is one year) on entry. It may be possible to obtain a six-month extension to the visit visa as long as the candidate will be maintaining visitor status, and there are good reasons to do so. It is sometimes possible to change status to another longer - term visa whilst in the US as a visitor, as long as the candidate advised the relevant US Embassy or Consulate of this possibility beforehand, or there was no pre-conceived intent to do so.
On the facts that you have provided, I see no reason that you should not be granted an extension to your trip. Also due to the fact that you own fixed property in South Africa, and you have family here.
If there is something more specific that you need clarity on, please continue in this same thread.
Good luck and best regards,
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