Is that indicator can only be used for short-term trade?
First of all, indicator works perfect during trends and oscillator works perfectly in the range market(or flat market). So, indicator can be used for long term, as well as short term. I mean if it is a range market, using this or any other indicator will not help much, so it you should consider market direction first.
If it can be used to long-term trade, is there something I need to change from the parameters used? like, only using SMMA(5,8,13)?
The parameters are there to change them. Of course you can change them based on your trading style.
Considering my statement above does not mean that trading is very easy. I never use indicators alone to make trading decisions. It is always good to use oscillator to filter out bad trading signals.