Do electrical circuit systems break down without use?
To answer your question... no.  Electrical circuits do not break down if they're not used.  Most common wiring is made of copper and doesn't break down over time.  Some wiring can be  aluminum but again, it doesn't break down.
However, to expand.  The connection points can corrode overtime, especially in moist environments, and create connection problems in outlets, switches and light sockets.  Depending on the connections you can clean these up with some steel wool or in bad cases get new switches, outlets, etc...  If you don't feel comfortable doing it an electrician is just a phone call away.
As well, animals (rodents such as mice, rats, racoons, etc...) can chew on wiring and cause major problems that you might not see.
Also, depending on the age of the building is the service amperage.  If you don't have enough amps you could be blowing breakers when everyone is using their hair dryer at the same time or the DJ/Band (if you are having one) starts plugging in their equipment.  Lots of older homes have two or three rooms connected together on the same circuit so this could be a very annoying problem.
So while the circuits do not break down, you can have a host of other problems.