NBC will shuffle its Tuesday comedy block again next month, moving the Disney sitcom “The Good Life” to 8 p.m. and bringing back Castle Rock’s “The Second Half” to round out the hour.Doubling up With “Good Life” moving from its 9:30 p.m. berth to lead off the night, NBC is expected to double-run “The John Larroquette Show” for a six-week period from 9-10 p.m. in an effort to boost the Witt-Thomas Prods. series — which, despite positive reviews, has consistently struggled against ABC powerhouse “Roseanne.” NBC will introduce “Good Life” to the 8 p.m. slot with back-to-back episodes March 15, with “Second Half”– which stars and is exec produced by John Mendoza — to return the following week. Shaky ground The series has been on hiatus since Dec. 14 and will get a four-week run to redeem itself after being on the brink of cancellation. The network, in fact, has enjoyed scant success with its attempt to establish a comedy beachhead Tuesday, averaging a 12 share for the 8-10 p.m. sitcom block. “Saved by the Bell: The College Years” and “Getting By,” two initial components of the block, have each completed their season but remain under consideration for next year. “Cafe Americain,” moved to Tuesday in January, is on hiatus.