Each game is different. You can only judge by player behaviour on the day.
For me you can't tell by how many sin bins you give. Don't give many, they will say you are too soft. Give a high number, the you are too card happy.
I personally don't like to give many and prefer to try and manage, but when they cross my higher threshold or leave me with no option then they are fair game.
The question you need to ask is more for your match control in general. If you feel comfortable the temperature of your games, then you probably have it about right. If its high towards you before you issue the sin bin and doesn't change then you need to up it. On the flip side. If it increases, after you give a sin bin, then may be you are giving too many.