crank limits
I do not have data for any specific commercial aircraft, but can cite an experience with a carrier-based Navy bird.
There was at least a 5-minute continuous crank permissible, as long as starter air temperature limits were observed. This was useful for a compressor wash procedure (not a bad idea in salt air environment).
However, if the hydraulic system were loaded (e.g. for wing fold/unfold), the duty cycle was much shorter. This made it impractical to use the starter to run hydraulics.
So it all depends on the installation characteristics.