Something as big as buying a house — let's plan it out carefully.
Tips
history
The phrase 从长 comes from 《左传·僖公四年》: '筮短龟长,不如从长' — when divination methods disagree, go with the more authoritative one. Later Yuan playwright Li Xingdao pairs it with 计议 ('to plan and discuss') in 《灰阑记》.
usage
Often a gentle way to refuse or defer: '这事从长计议' ~ 'let's not rush into this' (and often: let it drop).