My sons have two Guinea Pigs. Usually, on average, once a week, they need to be changed. Unfortunately, it can be a difficult task seeing as there is nowhere else for the little guys to go while you are doing that. In the summer, we can take the Pigs outside and let them graze on the back lawn. As long as they are supervised, they are fine. Unfortunately, one of them likes to randomly run for it. And he's a fast little guy. Makes it difficult, especially when he gets underneath something and we can't get him out.
In the winter, we have the same problem but indoors of course. And there are far more dangers in the house like stairs or the risk of getting tripped over if you don't know where they went. I had an old futon frame sitting in the garage for a long time that I finally took apart. There was a lot of good pine pieces that could be used somewhere else. In this case, I used the pine pieces to build the Guinea Pigs a large pen or 'Corral'.
There's more room for them to run around and investigate things in there. Guinea's are naturally curious critters who like to push light objects around or climb inside of things. After a few hours in the pen, they are ready to go back in their cage and sleep it off.