Septic system survival rate?

I'm looking into purchasing a home which has been vacant for 6 years. It has a septic system and a well. What are the ramifications of leaving these things largely unused for such a long period of time? Is the well likely to have problems? I've certainly heard that septic systems "go bad" after a period of disuse; can anyone confirm or explain this?

Thanks in advance; you guys are a veritable font of knowledge.