I intend to keep an SSH and a Minecraft server up 24/7 (with the exception of the monthly server update). My only problem is, the wifi just stops working after a few hours so I'll have to manually reboot it. This will not be an option in the future. Also, I must use Wi-Fi, as ethernet cables along the floor and in-wall wiring are not currently an option. And for now, neither is moving the Pi.
What wifi dongle are you using ? Edimax ?
Maybe you can change the power managment of your wifi USB dongle : https://www.raspberrypi.org/forums/viewtopic.php?f=26&t=6256&start=1125
Had a same kind of issue, ended up with a proper USB powering. Used exactly this hardware to mak it go away :
used a power-meter to find a volt-amp dumpings, and - used a power supply, monitoring it at the same time by using an additional USB powermeter
You could try using a fixed IP address. Maybe your DHCP lease is expiring.
It is a commonly known issue that if the pi is not powered properly , wifi and Bluetooth communication can be very finicky and have a lot of weird symptoms. While it is suggested to have at least a 1amp power supply, I would suggest a 2amp power supply in case you ever decide to add even more peripherals.
Disable power management on the wi-fi. See: https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=44044