@Ejazmp router lease time is 24 hours but device connected to range extender keep on disconnecting and lease time refreshing. Check screenshot.

  @Ejazmp Update - this issue is real. Not only dhcp lease time reseting, at that same connection drops and reconnecting. This is getting repeated every 10 to 15 minutes. This issue is seen only in 5 Ghz band. I have tried 2.4 Ghz, no disconnection issue observed. To rule out, if the issue is with my mobile or not, I have connected multiple 5 Ghz mobiles and all have same problem - indicating the issue is with extender itself. Also, to rule out if issue is with my main ISP router, I have made another 5 Ghz hotspot connected to extender, in that also all device connected to 5ghz gets disconnecting and connecting ever 10 to 15 minutes.. but no device getting disconnected in 2.4 Ghz band, indicating the 5 Ghz band of extender is faulty. 

I dont know how can i explain all this to technition, no idea if they will give me replacement or refund or my money got lost :(

If any one have similar issue, kindly comment below.