Replacing all windows at once may simplify scheduling and create a consistent appearance, but phased replacement can be sensible when budget or urgency differs by room. Prioritize failed units, water concerns, difficult operation, comfort problems, and rooms planned for renovation.
Get the details in writing
A trustworthy proposal should identify the exact product and installation scope. If a term is important to your decision, ask that it be included in the agreement rather than relying on a verbal statement.