When using moving average indicators, whats the duration do you view for better accuracy? E.g. 5 years, 2 years, 1 year, 6 months, 3 months or 1 month?

Moving average, like any other technical indicator should not be use independently. A 1 year moving average may indicate a buy but a 5 year moving average may indicate a sell. As what Gabriel mentioned, the smaller the MA date, the more sensitive the moving average so your action points will be more frequent, but if you're an investor looking at something more long-term and a stronger sign of action, it'd be recommended to look at longer MA's instead

There is no moving average that is "better" than the other. The most commonly used ones are 20 MA, 50 MA, 200 MA. Each have their own pros and cons. 20 is more for shorter term support, if the trend is strong the 20 MA will be supporting or resisting well.

50 MA is kind of like medium term and 200 MA is to see a longer term trend.