How often should we be testing for weak seals?

How often should we be testing for weak seals during conversion of our flexible plastic packaging? And how should we be testing the bags? We test at the beginning of a roll, the middle and the end. Pressure hand squeeze test. I will appreciate any ideas other manufacturers of flexible plastic packaging have.

We produce flexible packaging test equipment,

For bags, mostly use leakage tester, sample test for every batch.

i am fresher, please send detail to my email, i  can share you details, with photos will be better.

You'll probably need to determine a suitable frequency based on throughput, the nature of the product, the history of problems etc.

"Hand squeeze test" sounds somewhat subjective to me, though?

Perhaps you could standardise this to make it more objective - for example we use inflation to a set pressure with air followed by submersion in water to observe for any bubbles, an absolute pressure test (i.e. pump a bag up until it explodes) with a minimum acceptable pass threshold, and then a filled bag test where the pack is filled with liquid and designated amounts of weight are placed on top of it, again to observe for any signs of leaking.  

You can see this video :https://www.youtube....h?v=GP9QedvUpYg

This is how we check the leakage condiction.

Thank you to Berton and pHruit for the reply. Our packaging is more for bulk (wet and dry) food storage between 20 and 200 micron, not printed pouches or packs.  I was just wondering how often other manufacturers test a +/- 80kg roll. I realize it depends on the size of the bags making it a difficult question to answer but a general idea will suffice. We are a medium size business. 

Sorry, i am afraid this is out of our knowledge now.