This often depends of the material of the door at the property and how long it has been installed. uPVC doors can operate at optimal condition for 20-25 years, whilst composite or timber doors can maintain their integrity for at least 30 years.
If your property is an older home with an original front door that serves as a visual or aesthetic nod to its history, it’s best to check for signs of wear and tear, draughts around the door or the quality of its closure (i.e. does the door stick/ is it difficult to open and close?)
This can also apply to internal doors, which are less prone to weather-related damage but can age over time with continuous usage.
If the door isn’t experiencing any faults but looks out of place with the rest of the property, you can always replace the door for aesthetic reasons or to make the property more visually appealing.