When should i expect my family's history of renal failure to actually affect me?

Varies widely.: It strongly depends on the cause of renal failure in your family. Genetic disorders such as polycystic kidney, vhl, iga, apol1 & tuberous sclerosis can cause problems at a young age and should be evaluated and followed early. Failure caused by high blood pressure, atherosclerosis, & diabetes occurs in middle age & beyond, requiring diet, exercise & BP control. Its good to be proactive.

Depends: It depends if you family has polycystic kidney disease, or some other form of cystic kidney disease such as von hippel lindau or tuberous sclerosis. If you have elevated blood pressure or abnormal renal function then you might need a further workup; including renal ultra sound and maybe even genetic testing.