I went out of town unexpected and it's now been 8 weeks of fermentation instead of 2 weeks can my beer go bad? I want to know if it's ok to bottle still. It's a english brown nut ale.
With proper sanitation and handling, the beer is fine. At worst it might've gone sour. Pathogens can't survive even minor amounts of fermentation. No worries.
The other respondents know exactly what they are talking about. If you are very careful with your sanitation practices (and temperature control), you can easily get away with 8 weeks in the fermenter in almost all cases.