I know theres a lot of talk about "banner blindness" but what about "lander blindness" ?
Say you have a campaign that is going strong, how often are you rotating your landing pages?
Or do you just ride it out until performance starts to drop?
we usually just change it up when the performance drops, if it's working why fix it? As well we throw in other landers too see if we think it will improve performance and sales.
We have some landers that are in rotation for 2 years
Landers are WAY harder to burnout, it's usually a problem of matching them with the right banners and offers. We're doing it similar to what freddy described above me, when performance drops, we try new or modified ones.
Same as Matej, I got one lander I initially created in 2015 and its still one of the best for that vertical/geo combination 
But as Freddy says, you should change it once the performance start to drop.
Actually you should always do some split tests (give your main lander 80% and assign the rest to landers you test, this way you can always have some backups + I recommend the same strategy with testing new offers as well)
Landers get burned out slower than offers in my experience.