B737 Captain reported an Engine Oil Quantity Lo annunciation while at cruise. The flight crew continued the flight to the destination airport while monitoring oil quantity.

Narrative

I'm writing to advise of an interesting event. Aircraft X; ZZZ-ZZZ1. Cruising at FL 380; at XA20 CT; we got an instantaneous #2 Engine LO Quantity 20% and flashing white box. All other oil indications were normal; as well as engine. Prior to event; oil quantities were normal and matched closely. We assessed that we could end up single engine soon; and started looking for nearest suitable airports; if we needed to do that. Additionally; started to review QRC/QRH in preparation for a possible engine failure or shutdown. We coordinated with ZZZ2 Center; for a lower altitude and airspeed. Assigned FL 350; then soon after FL 320. Slowed to74. At XA30 CT; contacted (Company) Dispatch and advised them of our situation; also short conversation with Maintenance. He advised; follow QRH guidance.Top Of Descent; followed soon after; and we continued our assessment of possible landing airports as we monitored the #2 engine. The quantity slowly went down; but would tick up sporadically; then continue down; very slow. While on the arrival branch point; we decided to request preferential coordination direct to ZZZ1. Final approach it was reading 10%; then went to 6% at landing. Landed ZZZ1 Runway XXR uneventfully. While taxi back to terminal; it increased to 20% and remained there at shutdown. Our constant question was; 'what is the limit; zero; or a predetermined %; when the motor would fail?'The next day; I called Maintenance to ascertain if they had found anything out. Maintenance said they were still looking at it with GE Tech Support and had come across Main Bearing and Main Bearing Seal failure; but it wasn't definitive yet. He did tell me that oil was bypassing into another container or void space where it shouldn't go.