In regards to the addition of hydrogen to alkynes, does the amount of moles of Hydrogen matter?
Your question is not entirely clear, but I think that you ask whether or not an excess of hydrogen gas would interfere with the reduction of an alkyne to an alkane.

This is not the case. A lot of the time hydrogen is just drawn into the reaction flask directly from a large reservoir (20L $\ce{H2}$ gas cylinder under pressure or a simple balloon). When the pressure in the reservoir does not change anymore (in the case of the balloon when it does not shrink anymore) it means that the reaction is finished, i.e. no more hydrogen can be added.

In general over-reduction cannot be prevented by limiting the amount of hydrogen present. It will just result in an awful mixture of products (alkanes/alkenes/alkynes). A poisoned catalyst is required to prevent this (e.g. Lindlar's catalyst).