Pittman left the group after MMHMM's release (later going on to play with Inhale/Exhale), and John Warne (ex-Ace Troubleshooter) filled in on bass for touring purposes, becoming a permanent member in 2005. Relient K further added Jonathan Schneck as a third guitarist (who also played banjo and bells) that year, bumping them up to quintet status. With Relient K touring constantly in support of MMHMM, Apathetic EP followed in November 2005 as another treat to hold over fans as the guys readied their next album. Five Score Seven Years Ago (as in their fifth album in seven years), largely produced by Howard Benson (My Chemical Romance, Less Than Jake), was released in early March 2007. True to form, Relient K set out on a full round of nationwide dates, including spring shows with Mae and Sherwood, before releasing the Christmas-themed album Let It Snow Baby... Let It Reindeer (containing several tracks from the band's previous holiday release, Deck the Halls, Bruise Your Hand) later that fall. In October, Douglas announced that he would be leaving Relient K to dedicate himself full-time to his side project Gypsy Parade. He was replaced in early 2008 by Ethan Luck, who would accompany the group during its appearances on that year's Warped Tour. In July, the group released the B-side album The Bird and the Bee Sides, which was packaged with The Nashville Tennis EP. The band released its sixth studio album, Forget and Not Slow Down, in 2009.
Two seven-song covers EPs, titled K Is for Karaoke, Pt. 1 and Pt. 2, appeared in 2011. Later combined into one single LP release, K Is for Karaoke included their takes on hits from the likes of Cyndi Lauper, the Wallflowers, Cake, Toto, and Stone Temple Pilots. Their next set of original music wouldn't arrive until 2013. During recording, Luck parted ways with the band, his vacated slot filled a couple months later by the very drummer he replaced, David Douglas. The band's seventh LP, Collapsible Lung, was released that summer, peaking at number 16 on the Billboard 200. Their eighth effort would also fair well. Produced by Mark Lee Townsend, Air for Free featured the single "Look on Up" and debuted at number 44 on the Billboard 200, topping the Christian chart. ~ Steve Huey, Rovi