I have had the privilege of working for some clients for periods of up to 20 years in a row.
What this means is that I have been able to witness the effectiveness of methods I have used to repair, AND the longevity of the materials used. For example, clear silicone caulking used to seal a metal roof still going strong after 18 years in the sun and elements.
(this is good to know)
I have also witnessed other caulking, that was supposed to be premium quality, fail in less than a year. Since I perform a great deal of jobs requiring water proofing, I can confidently proceed knowing the history of my materials and methods.