Research is an art not a science with reproducible results. I have a good success rate and know many ways around inevitable brick walls. Results depend on many factors, mainly on what information you have and its accuracy.
Each generation further back may involve exponential increases in effort. I'll work within your budget, and time frame (higher rates for certain rushes). Completion is accelerated by the specificity of goals and information.
We can discuss your specific search options and estimates, as I evaluate your information and goals.