Has anyone had two teeth that had fillings/crowns both end up needing root canals?
Sure have! At this point, probably half of my molars have had root canals. The first one was the result of my dentist replacing a filling. He drilled out the old one and just kept drilling until he determined that all the decay was gone. Now get this!!!! After he was done, he actually said to me, "Do you feel lucky today". He thought that he maybe he went to deep and maybe could see the exposed nerve. Long story short. He refilled the tooth, I left, and 5 hours later (at 9:00 p.m.) I returned to his office crying hysterically from the pain that a "hot tooth" can produce. He ended up performing a root canal that night all by himself. So, yeah. . . I guess that I didn't feel lucky after all.
I also had a root canal performed twice on the same tooth a few years apart. The first one developed a small crack in the "material" that is used to fill up where the nerve was. Absessed tooth resulted. Pain was beginning to intensify. Other dentist had to remove "material" and additional nerve. Put on temporary crown and have not had any further problem with it.
If I knew that I was going to have so many problems with my teeth as I got older, I would have married a dentist for sure. BLING, BLING, BLING $$$$$