My wife and I live in a bungalow (built 1994) that has the original wooden window frames, every one of them with a trickle vent at the top (with double glazing). In the cold season, we get condensation on the window of the bedroom that we use. The condensation begins to appear almost as soon as the sun sets, well before we get in there. Last autumn I cut up an old towel to make strips, which I place on the affected window frames (at the lower edge of the glass) every evening. These don't prevent condensation, they just stop pools of water forming on the window sill. Putting them on is a bit faffy, but it keeps the worst of the moisture off the window frame.