Once you get to know your bike you will develop an understanding for where the bike is happy to shift. I ride a 2009 monster 696 and for me cruising below 3k the bike starts to lug and chug. When commuting I shift around 5k, but when joy riding I shift when the shift light flashes at me. Down shifting also depends, my 696 has a lot of engine breaking, and at low rpm the engine is extremely torquey so you need to be careful when you downshift. what kind of bike do you ride?