Floating content (FC) is a decentralized on-demand information sharing method with ad hoc communication among terminals. In FC, all contents are anchored to specific locations and shared among mobile terminals inside a predefined sharing area, which is referred to as an anchor zone (AZ), as if the contents float in the geographical area. However, contents may be vanished if there is no terminal holding the contents inside an AZ because the sharing procedure depends on ad hoc communication and infrastructure-based supports are not available. Thus, terminal density in the AZ significantly affects the content lifetime since there are less communication opportunities among terminals in sparse environments and disseminating contents are difficult. To address this issue, a method that adaptivel adjusts the effective radius of an AZ, namely the area in which information is shared with FC, has been proposed. The principle of the method is to expand the area according to the terminal density in the AZ. Although expanding the effective radius easily prolongs the lifetime of contents, unregulated expansion may lead to excessive and unnecessary dissemination. This paper proposes an effective radius adjustment and transmission timing control method to realise efficient and effective information sharing with FC. The proposed method employs terminal density and terminal encounter rate to estimate further communication opportunities. The simulation results show that the proposed method could achieve longer content lifetime with less overhead.