As my opinion, Everyone should create their own definition for “LONG TERM”.
My definition regarding “LONG TERM”:
1.Target wisely: Before investing only I decide the % of the return ( % should be realistic ) as per that stock strengths and weaknesses suggest in the technical set up and fundamental analysis. If your target of return successfully hugs you then again do all sort research, analysis regarding the stock to decide next target for return. If your analysis and research find still more worth and growth in that stock hold it. As per NITIN Sir said you should keep a stop loss even for profit. So, keep a stop loss for the next target of return.
Now, Coming to the diversification part watch this video of NITIN’s: https://www.youtube.com/watch?v=SuGU5niKawA