I remember a few years ago on here that several people agreed with each other that this tea rose was not much good (I am paraphrasing). I had 2 bushes of it in my garden at that time, and it is true that I thought it was rather wimpy, and not doing much - especially compared to other tea roses growing next to it. Here is a pic from 2000, when it was maybe 2 years old:

Over the years I have been vaguely aware, when occasionally I noticed it, that it was doing better and better. This Spring (yes, I know, 24 years later, but it has been doing very well for about 10 years) all of my roses are coming into bloom way later than usual. One of my bushes of Madame Berkeley just caught my eye today, so I took some pics of it. It is now about 6-7 feet tall, and 7-8 feet wide, and the blooms are much larger than they were in its first few years. About 12 years ago I also planted one in my niece's garden about 12 years ago, and it is doing the same.

I personally now enjoy several roses (the same actual plant, not counting the plants I have from rooted cuttings of ones which were originally planted 1905- the 1940s) which are about 50 years old. They were planted in the 1970s by my FIL. The survivors, mostly old teas, are healthy and gorgeous. I don't know how long it took for them to get that way, but I think it was worth it. I think MB is a rose which is a very slow starter, but over the years the blooms have gotten larger, as have the bushes, and it has bloomed more. If I had judged it in its first 3 years, I would have gotten rid of it. Here is what it looks like now: