I've been running the cable under the lid on my WSM since I bought the probe a few years ago. It's still working just fine. As long as you aren't deliberately abusing the cable and bending it 180 degrees or pinching it with a ton of force, it will be fine. Hell, I've left the unit outside overnight in torrential downpours and it keeps on ticking.
IMO, as long as you have a unit that reads fairly accurately, that's all that matters and you don't need to baby it. Granted, there are some mods you can do to fit the probe in other places, but I wouldn't stress out over it.