Yes roof windows get old and will need replacing!
When they start to leak, they course annoyance and eventually damage to other parts of the property.
If the Velux needs replacing I can do this in a few hours and when it is convenient to you or your tenants.
A damp roof may also be something simple like a cracked or slipped tile.
Velux windows come with a 10 year guarantee. This is what they to say, click here.