If you live in the northeast then adding more insulation would make a lot of sense - especially in the winter months as heating a house costs a fortune whereas you can always open the windows in the summer months. Adding more insulation now before winter comes will definitely lower your heating costs. Just be sure that you have the kraft paper side of the insulation facing the proper direction so you are not trapping moisture in your ceiling area.
You should see at least a 10-15% lowering of your heating bill this winter. Compare bills from last year when you get your bills this year. Now you can also lower the thermostat in the house and have a warmer home in the winter. I keep my home at around 63-65 degrees all the time in winter and my house is just fine.
Also, don't forget to caulk around your windows, even if you have done this previously as caulk will shrink on you after a few years. I use the new bioseal stuff (it can be pricey though) and found that it does not shrink up on me like other caulk/sealer. Be sure to seal/caulk under your home where the pipes enter the floor also. In the kitchen under the sink and in the bathroom under the sink and tub are good places also. If you can get under your home to do this sealing - great!! If you can't get under the home, you can still seal the areas around the water pipes and discharge pipes from the actual room. I did this a few years ago and I sure noticed a huge difference in how warm my home stayed.