  The Standard Model prediction of the $B_c$ lifetime is discussed, together
with the dominant uncertainties and strategies on how to improve them.
Furthermore, a new method to compute the $B_c$ lifetime based on the operator
product expansion is proposed. It relies on differences of $B,\,D$ and $B_c$
meson decay rates, in which the free-quark contributions cancel out, reducing
the uncertainty of the theory prediction.
