  Among dozens young pulsar wind nebulae, some have been detected in TeV
\gamma-rays (TeV PWNe), while others have not (non-TeV PWNe). The TeV emission
detectability is not correlated either with the spin-down power or with the
characteristic age of their central pulsars, and it is an open problem what
determines the detectability. To study this problem, we investigate spectral
evolution of five young non-TeV PWNe, 3C58, G310.6-1.6, G292.0+1.8, G11.2-0.3
and SNR B0540-69.3. We use a spectral evolution model which has been developed
to be applied to young TeV PWNe in our previous works. TeV \gamma-ray flux
upper limits of non-TeV PWNe give upper or lower limits on parameters, such as
the age of the PWN and the fraction of the spin-down power going to the
magnetic energy injection (the fraction parameter). Combined with other
independent observational and theoretical studies, we can guess a plausible
value of the parameters for each object. For 3C58, we prefer the parameters
with an age of 2.5 kyr old and the fraction parameter of 3.0x10^{-3}, although
the spectral modeling alone does not rule out a shorter age and a higher
fraction parameter. The fraction parameter of 3.0x10^{-3} is also consistent
for other non-TeV PWNe and then the value is regarded as common to young PWNe
including TeV PWNe. Moreover, we find that the intrinsic properties of the
central pulsars are similar, 10^{48-50}erg for the initial rotational energy
and 10^{42-44}erg for the magnetic energy (2x10^{12} - 3x10^{13}G for the
dipole magnetic field strength at their surfaces). The TeV detectability is
correlated with the total injected energy and the energy density of the
interstellar radiation field around PWNe. Except for G292.0+1.8, a broken
power-law injection of the particles well reproduces the broadband emission
from non-TeV PWNe.
