I have 28x78 double pane windows in my terrace doors that are 18 yrs. old.  Some of them have clearly started leaking, there is condensation inside (they have been leaking for several years).  They have a uv blocking film inside that also appeas to be loose.  I plan on rebuilding the doors and replacing the windows.  What is the best way to identify the highest quality replacements?  I would like to find a replacement that will last 20 yrs. without leaking...

Dave