If they are Morels you have a much better chance of success. Were they disassembled, inspected, cleaned and reassembled prior to being put in use?
Just a little reassurance maybe, the hydraulic roller lifters in my BBC were dead stable to 6700 on the dyno, and while I dont turn it that hard in the boat, it has been to 6200 many times. They are factory gm replacement hydraulic lifters. Good oil control and pressure is important.