What is it?
Are you running it hard when it quits?
Is it getting too hot?
What engine is in it?...What percent nitro?
Lots of different factors to consider when diagnosing "runs for about half tank and dies". I would assume first that you are running the hsn too lean, and it's overheating, and then the carb is vaporlocking.
It is common for the carb to have to be adjusted every day that you run it. Maybe even several times in a day if the weather changes, or if you change something else...Such as cleaning the air filter, or opening a new jug of fuel.
A temp gun can be a handy tool for learning tuning. As a general rule, most nitro engines run best between 230 and 280 degrees F. If they run cooler than that, the sleeve doesn't expand fully, and accelerated wear will occur...leading to sooner rebuild. If they run hotter than that, there isn't sufficient oil in the fuel to properly lube it...again leading to accelerated wear, and the whole rebuild thing...