In 2003, at age 46, Benoit won the Maine half-marathon, defeating a field dominated by runners two decades her junior, and she was faster than all but six men overall, finishing in 1:18. In 2006, she helped pace former cycling champion Lance Armstrong as he competed in the New York City Marathon. At the 2008 US Olympic Team trials, at the age of 50, she finished in 2:49:08, setting a new US 50+ record and beating her personal goal at the time of a mid-2:50s marathon. When she ran the New York City Marathon on November 1, 2009, she broke the Senior Masters record for runners older than 50 with a final time of 2:49:09. On October 10, 2010, she ran 2:47:50 for 43rd place at the Chicago Marathon—the site of her American record a quarter century earlier—missing her goal of qualifying for an eighth Olympic Marathon Team Trials race by 1:50, but recording the fastest-ever performance by a woman over 52. Later that month she ran in the Athens Classic Marathon for fun and finished in 3:02, the slowest time of her career; she was not fully healed from her Chicago performance. In April 2011, Joan competed in the Boston Marathon, completing the course in 2:51:29 and placing 1st in her age group. Between 2013 and 2015, Samuelson ran the Boston Marathon each year, and setting three of the four fastest marathon times for the 55-59 age group. None are recognised by the World Masters Athletics since the Boston Marathon course does not comply with IAAF regulations. Her times are 2:50:33 (2013), 2:52:15 (2014), and 2:54:26 (2015). In 2019, Benoit ran the Boston Marathon again, forty years after her 1979 win. She had hoped to be within 40 minutes of her 1979 time, but did even better than that with a time of 3:04:00, within thirty minutes of her winning time, again winning her age group (60-64).