Don't replace; restore!
Did you know that under all those layers of paint, your original Victorian and Edwardian windows and doors are constructed of tight-grained, old-growth redwood and Douglas fir? Antique windows in this region are always built from of old-growth heartwood, the finest rot-resistant lumber ever produced and sadly now, quite rare.
Replacement windows constructed of softer, non-rot-resistant farmed wood won't last a fraction of the time that your original ones will. Save money and preserve the traditional character of your home by restoring rather than replacing these valuable features.
Given the proper care and maintenance, a quality antique window can last for centuries and even be upgraded to meet contemporary energy-saving goals with simple treatments. Don't be persuaded to replace these jewels of the past with plastic or inexpensive softwood components that have a comparatively limited lifetime.
Check out this great article on restoration vs. replacement: 5 Worst Mistakes of Historic Homeowners (Part 1 Windows)