  The fallback disk model is widely accepted to explain long-period neutron
stars (NSs) which can't be simulated by magnetic dipole radiation. However, no
confirmed detection of disk was found from the newly discovered long period
pulsars GLEAM-X 162759.5-523504.3, GPM J1839-10 and the known slowest isolated
NSs 1E 161348-5055. This might be that the disks have either been in
noninteracting/inactive state where its emission is too weak to be detected or
have been disrupted. In this work, we conduct simulations to examine the
lifetime of supernova fallback disks around isolated neutron stars. We assume
that the disk's mass varies in a self-similar way and its interaction with the
NS occurs only in interacting/active state. Our results reveal that nearly all
the interacting lifetimes for the disk are shorter than 0.1 Myr while the
existence lifetimes are considerably longer.
