Break in time for Tung-Sol 6550 Tubes

What is the break-in time for a NOS Tung-Sol 6550? I wanted to see if a NOS grey-plate, Tung-Sol 6550 would be an improvement to replace the original Sovtek 6550 I was using in my ARC Ref 6. When I first put it in the sound was bright and edgy—not the least bit musical. Someone in this forum mentioned that these tubes take 200 hours to break in. So—I actually took the time to keep it in my system for what is now about 100 hours, and I did notice a big difference. The midrange was improved, with a sweeter, richer sound. It is now at the point where this tube is acceptable—but there is still a trade off when compared to the Sovtek. The Tung-Sol has a deeper, tighter bass, more extended highs and a decent mid-range. Overall, there is more detail—a cleaner sound. However, the Sovtek has a much fuller sound with a rich, sweet midrange—but not as open. I am still not completely sold on the Tung-Sol, despite the big improvement when it had more break-in time on it. My question now is--will the additional 100 hours of break-in time make that much more of a difference in creating a warmer, richer sound?