If they are out of the term/lapsed is one able to file a new patent? Further, is it against the law to use a very similar description, or does my description have to be totally new?

The invention covered by a "lapsed patent" is, by definition, in the public domain.

You can not patent an invention that is already in the public domain. It has become "prior art", which on its face is not patentable because it is not a new invention.

Ok good to know. So if its public domain it is free to use?  I'm talking like 4+ years of being lapsed.

Or I could make it similar and add some additional functions and I could then patent that?

If you had some "novel" and "useful" additions to the previously-patented material that were not "obvious", then it is possible that you could patent those. But the whole world could still make or use the prior patented material without owing any royalties to anyone, and nobody could legally prevent them from doing so.

Interesting. So basically if you patent something and you do not keep up with the patent status, you are no longer able to sue for infringement?

Say I patented Item A. I let it lapse. After that point anyone can use the information.

I then come up with  Item B, it includes the functions of Item A, but then I also include "novel" functions not found in item A.

I am only able to sue for infringement, should someone decide to come up with their own version of the item, including the functions that are protected under Item B patent.

If they only decide to make Item A (from the lapsed patent) I am SOL?

Appreciate your time and responses.  

That is my understanding.

BTW, I am not a patent attorney and do not work with patents for a living, but I did pass the USPTO patent bar exam way back in 1992 (and became a "registered patent agent"), although I let my registration lapse long ago.

A good book that explains all of this is "Patent it Yourself":

http://www.amazon.com/Patent-Yourself-Step---Step-Filing/dp/1413317197/ref=sr_1_1?s=books&ie=UTF8&qid=1395621682&sr=1-1&keywords=patent+it+yourself

(A newer edition is scheduled to come out later this year - IIRC there have been some recent changes to US patent law, but a lot of the underlying concepts should still be valid if you refer to older editions of the book).

Chromekilla-

You are pretty much right.  First, I assume you mean the patent has expired rather than lapsed for failure to pay a maintenance fee.  IF you do mean lapsed rather than expired, you generally can revive the patent so long as you are within 2 years after the initial time to pay the maintenance fee and it was unintentional.

Regarding your scenario, once the patent has expired, you can no longer sue for new infringements.

Chromekilla,

If you can get a patent on invention A+B, then that patent stands independent of the patent (lapsed, expired or otherwise) for invention A.  The trick is getting the patent for invention A+B.

Patents are not renewable.