You should regularly close all background apps running on your phone to preserve battery life.
Modern mobile operating systems (iOS and Android) implement sophisticated app suspension: backgrounded apps are frozen in memory, consuming negligible power. Aggressively closing apps forces the OS to completely relaunch them when you return, requiring disk reads, reinitialization, and network reconnections, all power-intensive operations. Apple and Google have publicly stated that force-closing apps wastes battery and diminishes performance. Users observed this when iOS 13+ introduced auto-refresh controls; leaving apps suspended actually improved battery life compared to manual termination. The behaviour persists due to decades of PC-era habits where closing unused programs freed RAM, a different optimization problem on resource-constrained phones.