I wouldn’t overestimate the “strengthening” effect of increasing exposure time. Resin is either solid or not. (There are a few stages of “not” ranging from “slimey” to “watery”, but none of them are structurally sound).
The main thing you get from longer exposures is a bit of insurance in case there are variations in layer thickness (e.g. first layer, or structures not fully straightening out after flexing).
Long exposures will cause a softening of XY resolution and Z “blobbing” to a variable extent depending on exactly how long we are talking about and how much pigment you have in your resin.
