According to the SEC, the Dodd-Frank Act does not require the SEC to bring an enforcement action within 180 days of issuing a Wells Notice.  See

Although the Dodd-Frank Act amended the Securities and Exchange Act of 1934 Section 4E(a)(1) to require the SEC to bring the action within 180 days, the SEC said it was not applicable since Congress never said what the consequences if it failed to do so.  The SEC claims to be relying upon precedent from other admiminstrative agencies.

We do not believe this issue is over, and either the courts or Congress will weigh in on this issue.  That means, stay tuned!!