Most strings should last quit long, but some time can broken quickly, there could be many reasons.

Strings loose tension, should pre-stretch string?

"Pre stretching is where you tighten each string to a higher tension before tightening it to the correct tension. The idea behind this is that you remove any elasticity the string has inside of it, meaning that it will hold its tension for a longer period."

we can have 0%, 5% or 10% pre-stretch. I won't pre-stretch if you don't ask for

Pre-strench may keep the tension better but may last shorter.

Where it’s more likely to be broken.

In the  middle.

Mostly the strings should broken in the middle, where the sweat spot is, the here should be mostly you hit the shuttles.

Top sides

This is also quit common , the reason is racket touch the floor

anywhere from sides, or the main string getting stressed when smashing.

This can also happen when the grommets broken (SEE THE PICTURE), higher tension more likely cause grommets broken, once the grommets broken, the strings will contact with frame directly, the frame may cut string with 1 hit close to there, or can broken when string it. And even can break itself without playing

What should you do when string broken?

Generally you need to cut strings straight away, as broken strings cause unbalanced stress to the frame, can damage the frame especially with higher tension.

But it also depends on where and which strings are broken: 

Mains broken

The strings have mains and cross, the mains are the striainght ones, and they’re more likely to be broken as they getting the power when smash. This will need to restring and cut the string straight away. keep the broken main strings, the frame get stressed

Cross broken

it's quit offten broken at the top side, normally this part wont’ affect frame much, don’t have to cut them, and this is the last part when stringing the racket.

If broken in the middle, more liked need to be cut as the string mostly are wore out.

Any other place for the crosse, don’t have to cut if it’s new string as could be get repaired.

How to repair…

Can cut the broken part,  make a knot , and add extra strings needed.