The efficiency of consuming a working substance in the cyclotron arc ion source during operation at the LNR JINR cyclotrons is analyzed in comparison with the results obtained for the ECR ion source of GANIL and the Berkeley cyclotrons. The experimental results described have been obtained during the acceleration of rare isotopes ion beams (Mg-Ge) at the U-400 and U-300 cyclotrons. Some features of solid working substances fed into the cyclotron ion source are described. The optimal conditions for the efficient use of working substances in the arc discharge are discussed. The results of producing and accelerating rare gas isotopes ion beams, including the radioactive isotope carbon-14, are presented. Prospects for the future development of efficient ion sources for the LNR cyclotron complex consisting of the U-400 and the U-400M are also discussed.