[sd79812]

Searle’s bar experiment measures thermal conductivity by comparing temperature differences near the heat source and at the ends. However, since the temperatures at the unheated end/heated end often equalize at the beginning/end, the experiment may seem to take an indefinite time to yield results because you can't divide by zero, and I know for a fact that fraction can't be zero so often.

[Borek]

To be honest I have no idea what you mean. Temperatures can't be equal if one end is heated and the other cooled.

Experiment time is not defined, but you should take measurements till the system gets to thermal equilibrium - that is, consecutive temperature measurements produce identical results.