  In this paper the thermal stability of skyrmion bubbles and the critical
currents to move them over pinning sites is investigated. For the used pinning
geometries and the used parameters, the unexpected behavior is reported that
the energy barrier to overcome the pinning site is larger than the energy
barrier of the annihilation of a skyrmion. The annihilation takes place at
boundaries by current driven motion as well as due to the excitation over
energy barriers, in the absence of currents, without forming Bloch points. It
is reported that the pinning sites, which are required to allow thermally
stable bits, significantly increase the critical current densities to move the
bits in skyrmion like structures to about $j_{crit}$ = 0.62 TA/m$^2$. These
currents are similar to those obtained experimentally to move stable skyrmions
at room temperature. By calculating the thermal stability as well as the
critical current, we can derive the spin torque efficiency $\eta$ = $\Delta/I_c
= 0.19 k_BT_{300}~/\mu$A, which is in a similar range to the simulated spin
torque efficiency of MRAM structures. Finally, it is shown that the stochastic
depinning process of any racetrack like device requires extremely narrow
depinning time distribution smaller than ~6% of the current pulse length to
reach bit error rates smaller than ${10^{ - 9}}$.
