The big problem with browser stats is that they are averaged over a day or month. Maybe not an issue with a global audience, but for a local audience you find desktop use is mostly limited to between 8-6 while people are at work. Mobile spikes during the morning and late afternoon commutes and tapers off into evening. Tablets have a smaller morning/afternoon spike and gradually pick up in the evening. This is fairly consistent over a number of .com.au sites I have analysed mobile traffic for.

So, at the time you're running your evening TV advertisement or PR spot it's 80% mobile, not the 25% the stats tell you.