elimination of the 5 year remedial cycle

Can anyone explain the rules moving forward in plain English (after the elimination of the 5 year remedial cycle)? 

I cant seem to find anywhere when is necessary to restate and FTW is not much help.

Thanks in advance

It sounds like the plan at issue is individually designed.  If so, and if you already have your first letter, and the plan is not terminating, then unless things have changed since I last looked (and I don't think they have), you can't get a letter.  

The requirement to restate was a condition of applying for a letter.  There is no requirement in the tax code or ERISA to restate.  Since you can't get a letter, there can be no requirement to restate as a condition for a letter.  

I agree with ERISAPPLE and would also recommend never restating, no matter how many amendments you have over how long a period, unless the IRS decides to issue DL's again to continuing plans, e.g. in a window after a major law change. The reason I recommend never restating is that, in any sort of review of your plan documents, whether an IRS audit, review by independent auditor, or due diligence review in an acquisition, you will be better off having, as a separate document, the last executed plan document that had a favorable DL, and then all your executed amendments, even if those become numerous. In that way, review will be limited to the amendments and it will also be very clear which document is the subject of the letter. For administration purposes, you can prepare an unexecuted "working copy" that is effectively a restated document, but I would recommend not adopting that "working copy" or executing it.

As stated by the previous responders, there is no "maintenance" determination letter program currently in place for non-preapproved plans, and thus no need for periodic restatements.  You may be interested in the Section called " Recommendations Regarding Re-Opening the Determination Letter Program" in the committee report at:

https://www.irs.gov/pub/irs-pdf/p4344.pdf

Sorry for adding this so late - practitioners need to examine the annual IRS List of Required Amendments for non-preapproved plans to see if amendments are required.   The Procedure details when such amendments need to be adopted. I don't recall the timing - I think three's a lag in getting things on the list (I believe the IRS waits until sufficient guidance was issued, so a new law is not necessarily put on the list as soon as a new law is enacted), and I think there is then a window after the item is added to the list for making the amendment (which I think is two years).  (Don't take my word for it on my parenthetical recollections.) You also need to determine whether the document needs any of the amendments on the IRS List (it is a case-by-case determination, i.e., not every amendment will apply to every plan).

Restatements are now viewed by many  practitioners (such as Luke) as being not recommended (at least for plans with a determination letters). Other practitioners might reasonably conclude that any challenge (upon IRS audit) to a particular provision in a restatement can (hopefully) be defended (from the need for retroactive correction) by demonstrating that such language was in the document when the document was last approved. I am not voting one way or the other. I would say that the "separate amendment only" approach appears to me to be the majority view (based on conversations I have heard). Another way of looking at this is that every amendment (whether required or discretionary) must be perfect (unless you are using an IRS model amendment), and there is no way to obtain a guarantee short of obtaining a "private" letter that the plan is properly drafted, in which case, you might have recourse against the party providing that opinion if that turns out to not be the case.

One more thing:  the IRS publishes an annual Required Amendments List.  You need to update the plan for the items on this list by the end of the second calendar year following the calendar year in which the item appears in the list.  So, while you should not restate, be sure to update on an annual basis if there's something on the list that affects your plan.