Four winters of film, same three windows, and the difference between "amazing" and "fell off in a week" is almost entirely the tape and the surface under it.
What actually matters:
Clean the frame properly and let it dry. Not a wipe — the tape is fighting years of grease and dust, and it will let go in exactly the spot you skipped. This is the single biggest cause of the one-week failures.
Old paint is the real enemy. On flaking or chalky paint the tape takes the paint off rather than sticking to it, which fails and damages the frame at the same time — the worst of both, and worth knowing before you start in a rented flat. Test a short piece somewhere hidden and pull it off before you commit to a whole window.
Tension it with heat, patiently. The film goes on loose and deliberately baggy, and a hairdryer shrinks it flat. People stop too early because it looks fine, and a slightly slack film flutters, which is what makes it read as cling wrap. Taut, it is close to invisible and you stop noticing it by December.
Leave a small unsealed gap if the window shows heavy condensation. Fully sealing a window that was already streaming can move the moisture problem behind the film where you cannot wipe it, and then you are growing something on the frame instead.
Cost is genuinely small — a kit does a couple of windows and lasts one season. The honest limitation: you have sealed the window shut until spring. In a bedroom you actually ventilate, that is a real trade rather than a detail.