The truth that nobody wants to really admit is that there's simply no way to keep a determined hacker out of a wireless network. It's, by its very nature, an open network. About the best you can do, short of going wired, is regularly rotate your wireless passwords (get a new one every day, for example), and also maybe set up a VPN on your local network, so that even if you're on the wifi you can't actually do anything with it without connecting to the VPN.
Are you thinking of WEP encryption? If you are using WPA2 encryption, asking someone to change their password once a day is completely unreasonable.
If you are using WPA2 and a semi-long password there is absolutely no need to change the password daily. The way that cracking WPA2 works is by capturing an authentication handshake of a user who knows the password, storing that locally and then cracking it on the local machine. Now you are playing the waiting game, even if the attacker was using (http://arstechnica.com/security/2012/12/25-gpu-cluster-cracks-every-standard-windows-password-in-6-hours/) cracking at 350 billion passwords attempts a second, a password with 20 characters (upper, lower, digits, and punctuation) would take
(32 lower + 32 upper + 32 punctuation + 10 digits) 104 ^ 20 = 2.1911231430334195e+40 possible combinations.
2.1911231430334195e+40 / 350,000,000,000 attempts per second would require 62,603,518,372,383,410,015,659,322,218.865 seconds to try each combination. Which comes out to a potential 2,905,645,676,789,197,589,949.8015733293 years to crack. Change your password once a year and call it good.
Wireless networks are not open by nature, they are broadcast by nature. There is a very big difference.