replace windows and/or doors

When is the best time to replace windows and/or doors in your home?

There are various factors that can be indicative of replacing windows or doors. First of all, it is functionality, ease of use. Could it be repairable?

For me, the increase in payment for electricity in the cold season was indicative. I studied why this happens. And I found out that there were large heat losses in my house. Both windows and exterior doors were my scourge. After that, I decided to replace my old windows with exterior doors. And this winter I realized that I made the right decision.