Following Mr. Wizard's suggestions, I'll offer the following comment to the OP's situation in an attempt to summarize the communal wisdom on this point.
The great difficulty in the OP's question is in timing the rendering process, which takes place in the Front End and vastly overshadows the calculation time in the original problem. Unfortunately, there is no (documented/known) way to do that so far.
I also think, however, that the whole point may be moot. If the situation is such that rendering overshadows computation, then one should consider pruning the data set being plotted because it is likely to be too detailed to be meaningfully presented at common resolutions and sizes, as kettern also mentioned.
In this connection, one can make judicious use of the
MaxPlotPoints option for the list plotting functions to downsample such a data set automatically (its documentation states that "the total number of points plotted is reduced by combining nearby points"). Oleksandr and Mr. Wizard mentioned it in comments as well.