The attic is generally not a part of the house that sees upgrade a lot because it is not someplace that people use frequently. It is generally used for storage but once in a blue moon, it does see an upgrade and if you are planning to do just that, we would recommend that you insulate it.
If you talk to professionals at https://goo.gl/maps/ht3nNkagexx, they would tell you that insulation of an attic is absolutely necessary. You might think that your attic is perfectly insulated as it is but you cannot know for sure until and unless you get it insulated. You can check for signs that will tell you that at least an inspection is needed to check the insulation of the attic.
If you have suddenly noticed a spike in your electricity or gas bill amount then it can indicate that somewhere, energy in high amount is being consumed. This points to one thing i.e. poor insulation and the only way to fix it is to get new insulation in your attic since its insulation can affect the whole house.
If you feel that whenever you are in your attic or standing directly under it, the temperature is cooler there than other parts of the house then it means that you need to get it insulated properly.
When you enter your attic and touch its walls, do you feel that they are a bit damp? If yes then it is a sign that insulation is needed desperately.
Drafts of Air
You need to stand in your attic for a while and try to see if you can feel any draft of air as that will be an indication that there are gaps somewhere that need to be insulated.