I have used professional researchers 3 times, all with great success!
First, my great-grandfather was a railway stationmaster.
I employed a railway specialist researcher at Kew to find information on his career.
Second, my Great-Great-Grandfather was born in Jersey, Channel Islands.
I paid a researcher at the Channel Islands Family History Society to find records of his birth, and his family.
Lastly, I had to employ a researcher to provide proof to Guinness World Records of our claim to the joint record of Most Successive Generations of Twins. Had to be done by a Professional, even though I provided all the records!!