No — it's definitely not necessary to flush your coolant with every change. Some shops might recommend it but a regular drain-and-fill will work fine. Flushing your coolant every time is a waste of our time and your money.
That said, we recommend following your owner's manual. If it gives a timeframe for a full flush, stick along those lines.
Or if you've got an older truck, a full flush is going help keep debris out and prevent reust and corrosion.
Like all regular maintenance, neglect will cause poor performance.
Stick to your regularly scheduled maintenance and you won't have to worry about looking out for problems.
BUT — if it's been a while and you've been neglecting your truck, the following issues might mean you need a flush:
You'll definitely want to bring in a new vehicle around the 75,000km mark.
After that, coolant flushes should be done once every 50,000km. — which is to say every few years depending on your driving.
Obviously, stick to your manual's guidelines but this gives you a rough idea.