Depends really. I probably do once a week for 2 guinea pigs together and twice a week for more than 2 guinea pigs in a cage. If I see a particular part of the cage gets bad I will always clean it out. I use carefresh at the moment which lasts much better than woodshavings e.t.c
perhaps my three are spolit because I clean them out every other day. There are three of them in one big hutch though. They also have an indoor run to play in.
For the hutch I use newspaper, then shavings, then hay. For the run I have an old bit of carpet and I put a puppy training mat on top of it at one end. The guineas are really good because they mostly go to the lav on the mat so it's easy to clean!
my lot are cleaned out sometimes twice a week, depending on the condition.. the hutch/cages then get spray with deodorising pets spray, then ablack bin liner is putat the bottom,, followed by newspaper, woodshavings and hay.. they also have some shredded paper in there too if I have any..
When they need cleaning out again I only have to grab the liner from the bottom, fold it up and chuck away!
I think it all does depend on which bedding you use. Woodshavings doesn't absorb urine aswell as carefresh. I am going to try some other bedding when I have made the C&C cage which Kate recommened. Can't remember what it was though!
I clean the poos out everyday from the three male cages and remove all the bedding and hay from the mum and babies everyday, but with the others, I properly clean them out twice a week. I can't do it just once a week as they it would get hanging
I clean my piggies house where they sleep every day and poo pick the run, it usually takes half an hour I don't work though so I have alot of time on my hands and I like chatting to them as I am cleaning them out