What you remembered is essentially correct.  Multi-year construction contracts (e.g. IDIQ) that contain options that would extend the term or time for performance of the contract do require a new wage determination at the time the option is exercised.  However, depending on which clause is in your contract (could be FAR 52.222-30, 31 or 32), the contractor or government may or may not receive a price adjustment based on the new wage determination. 

On the other hand if the construction contract (or task order) is fixed-price (and not a multi-year IDIQ), the wage determination that was in the solicitation at time of award will be the prevailing wage rates for the entire term of the contract even if the current contract completion date is extended.  The one exception that I'm familiar with is if you added work that is out of the scope of the contract.  Then, the new work would require a new wage determination. 

The DOL link below briefly discusses modifying wage determinations, but it may be worth contacting your regional Labor Advisor to determine if any other exceptions might apply particularly given the higher inflation in the economy today.

https://webapps.dol.gov/dolfaq/go-dol-faq.asp?faqid=348&faqsub=Wage+Determination&faqtop=Wages+%26+Work+Hours&topicid=1