The MA period length is determined by your trading style andf time-frame. if you plan to trade over 3-10 days, a 5 year daily MA will be irrelevant. Likewise for a long-term buy-and-hold investor who wants dividend income, a 14 day MA is just noise.
There is value in using multiple MAs - a short MA to help highlight entry points (though price action gives the real entry signal, not an indicator) and a longer MA to confirm trend direction and strength so you can be more sure you are following the majority of market players. Adding more MAs should mean you are following more distinct groups of market participants who have different time horizons. If they're all buying, you should probably be long (for which, read 'already long').
In all cases, the MA is a lagging indicator - it depicts what people used to be doing in this market: if that's not too much of a disadvantage to your style, that's fine, they have their uses.