As if it weren't totally obvious, I think that five minutes is just the right amount of time to practice when anyone is first starting guitar. If I need to say this a thousand times, I will. If you are beginning guitar, you do not need to practice an hour a day. You do not need to practice a half hour a day. Just five minutes. Form your own opinions, but I have my reasons:
1. Five minutes is about all the concentration that we might have at a brand new pursuit. It's more important to be casually interested in it at first, and allow the interest to grow in time as we get better at it.
2. Playing guitar is very much about escaping reality. That concentrated five minutes will help you get that in a small dosage. I think guitar can be pretty addictive after time passes, once a person reaches the point where two hours can go by and they didn't notice it. Five minutes is not a strict amount of time, but the point is not to overdo it.
3. Five minutes is hardly drudgery. On the contrary, an hour of "practice," really hard practice, will suck if you aren't into it yet, or just want to have fun doing it. I clearly remember times when I hated practicing. It just wouldn't flow. When you are trying to have fun, "No Pain No Gain" doesn't apply.
There are teachers who believe that practicing an hour a day is neccesary in the case of a beginning student, but I disagree. I firmly believe that if someone wants to have fun, they can get away with just taking the small amount of time to do it every day, and that's it. If you are planning on playing a show, or perhaps majoring in music, then maybe five minutes isn't enough practice. Hours and hours of practice? It's pretty indicative of a professional musician. If you want to have fun? Five minutes. Five good concentrated minutes. That's about all.