Mathematica can export time delays between frames together with the animated GIF (see "DisplayDurations" in GIF options). This allowed me to produce the 28-frame animation of the 28-cell honeycomb decay. Radioactive decay models intervals between clicks on a Geiger counter which are approximately exponentially distributed. The frame delays can then be calculated as follows. They are rounded and shifted to run from t1/100 seconds and have the average (t1+t0)/100 seconds.

delays[{t1_, t0_}, n_] := t1 + Round[ RandomVariate[ExponentialDistribution[1/t0], n]]