USS Miami is a 688i class boat, service life of 42 years with an extra refueling.
“The 18 SSN-688 class submarines that will be refueled at their mid-life could make good candidates for a service life extension because they could operate for nearly 30 years after the refueling. After these submarines serve for 30 years, they could undergo a 2-year overhaul and serve for one more 10-year operating cycle, for a total service life of 42 years. The cost for the additional overhaul of SSN-688 class submarines would be about $406 million per boat.”
http://www.fas.org/programs/ssp/man/uswpns/navy/submarines/ssn688_la.html
42 years?
Fix it up!