The only other thing I can think of is another common problem that some laptops have, windows has trouble with USB and
Mini-PCIExpress (Fucking tarded names) slots sometimes when combined with sleep mode. Often manufacturers will simply use internal usb pinouts for wifi cards and stuff. This means your laptop wifi card may basically be a USB compatable card, simply crammed inside.
Maybe try going into power options and turning off the USB power save suspend thingamajig (You'll have to go through a cascade of options, but it's there). That might fix it. And perhaps the differing wifi shutof times you noted were due to your changing power profile habits (Turning on or off USB or Mini-PCIE powersave options depending on what profile you happened to be on)? Worth a try.
Other than that cheap laptops (Like mine and yours) are literally designed to break, I fixed mine however and now it's great.
Seriously though, try both even if you don't think it'll work.