The autodetachment of 1s2s2p 4p0 in He- and nsnp 2 4P(e) in Be- (n = 2), Mg- (n = 3), and Ca- (n = 4) is calculated using an extension to continum processes of the multiconfiguration Hartree-Fock method. The main interest is to investigate the processes giving rise to long-lived, metastable states in negative ions. In He- and Be- our results agree with earlier experimental and theoretical ones, and do predict a long-lived component. In Mg- and Ca-, however, we do not find any corresponding long-lived state. The processes behind the decay of these states are investigated, and a comparison of the different systems is made.