There will always be somebody to try it since the begining of time. Icarus? 
He who shall not learn shall not fly, old indian proverb 
Then you obviously didn’t do your homework then…
I propose a closure of this thread since we have provided the poster with a bunch of recommendations that are useful for increasing flight time. They seem to be close-minded and unwilling to change anything about their aircraft - but somehow want a drastic 2-3x improvement in flight time.
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For example? List me some of the useful recommendations…
Well you got the wrong motors. So in that case you’re stuck with what you got. Can’t squeeze blood from a rock. Physics are against you sir, sorry.
If you want more fly time you need slower motor, higher voltage and bigger props, if you don’t want to do any of this you’ll never reach your target, no matter how many times you’ll ask