We got new blinds and curtains in our house 10 years ago. I can't take the blinds off the rollers so I sponge then with a wet cloth every so often. One blind is full of marks and flies. In summer we have bedroom windows open but dh still likes the blinds pulled down at night. This blind still works but is gone unsightly so I have to get a new one.
The curtains are full of mildew marks, despite having adequate heating and ventilation. We use mainly the blinds and only pull across the curtains an odd time in winter. Mayve if I pulled the curtains across every evening it may prevent the mildew.