Not just gamedev, particle physics data processing (my current job) is the same. Some fixes look so simple, rather interface than core but suddenly require a major core re-working. Some look so hard and complicated but require nothing except the device operator's guide and Least Squares approach. Describing typical task's difficulty as a damage, I'm sure it's far from Gauss' and I think it's 3d9 * N where N is the expected difficulty. Or even 2d11.
I afraid of two things:
1) Big overhead. Sometimes, job manage can take more time than the job itself.
2) Sometimes I can get suddenly busy for an unpredictable time. For example, it took half an hour to write this post. I've got four incoming calls about a photocathode strobe correction, sensor calibration ETA, my own analysis software setup (twice)... sorry, +15 min because of 5th call. Yesterday "one-evening" update led to a stability loss.
But spacemarines do not surrender.