if this is a shimano QR hub generator then the correct adjustment is a tiny bit of free play in the bearings that just disappears as the QR is used to fully tighten the wheel in the frame.
If you have finger tightened the cones and then tightened the locknuts and QR on top of that then the bearings will likely be seeing a monster preload and will be merrily destroying themselves.
If you adjust the cones so there is free play when the QR is tight, and increment (in very small amounts) towards a tighter setting, each time suggin gthe locknut down and tightening the QR, you will avoid having a monster preload on the bearings. The first time there is no free play (with the QR tight) you are done.
cheers