It's a common problem and common misconception. I'll worry about it next year, when it becomes a real problem.
That won't work. If he uses his existing Windoze 7 activation code for the free upgrade to Windoze 10, the Win 7 license will magically expire in about 30 days. I'm not sure about the 30 days part, but I do know that his Win 7 will become deactivated after using Win 10 for some amount of time. I've never had anyone try it so methinks it's wise to double check this.
Win 10 seems to need better and faster hardware than Win 7. If the hardware is 9 years old, Win 10 may not have drivers for everything. I say "may" because, except for video cards and printers, I haven't had much of a problem with Win 10 upgrades on older equipment.
The fans will stay quiet for perhaps 3-6 months. Most fans on the market use some form of bushing. The one's that say "ball bearings" are usually bushing. There are some magnetic levitation "bearing" fans (Corsair, CUI, etc), but most are cheap sintered bronze bushings. When the oil either turns to tar or leaks out, the bushing wears out. When you re-oil it, you fill the gap between the shaft and bushing with oil, but it doesn't last because the shaft hole in the bushing is worn and has enlarged. You can continue oiling it, but the oil won't stay in the bushing. I suggest you buy a new fan and start over.