Aside from the controversy about health problems, this was a poor insulating material in the first place. It was initially given a high R rating, but was subsequently down graded sixty percent by the Canada Mortgage and Housing Corporation, because it tended to shrink and leave gaps in the insulation.
Studies have shown that the reason the formaldehyde gas is released from this foam is either inferior materials or improper installation conditions (the mix, the temperature, the humidity). If a specific application is going to deteriorate, it will do so quite rapidly. If you have a wall full of this foam and have experienced no deterioration problems in the first year, you probably never will. Hundreds of houses that were monitored for gas diffusion showed little or no signs of formaldehyde. Some areas of the world never banned its use. Some areas have re-legalized it after the media "scandal" passed. When looking at the scientific data, I was a bit shocked to learn that two heavy smokers produce more formaldehyde gas than was measured in any of the "problem" houses. It is my opinion that a lot of people lost a lot of money through damaged property values in a scandal that had more to do with the media than with scientific reality.
If you have urea formaldehyde insulation in your home and you want to set your mind at ease, short of digging it out of the walls, you should perfect your air/vapour barriers as much as possible and install an air-to-air heat exchanger (HRV) central ventilation system. That will keep most of the bad stuff in the wall from diffusing out; what does get through will be taken away by the ventilation. Sealing and ventilation is the key to solving household pollution problems, even this one.
The National Research Council of Canada Building Practice Notes No. 19 and No. 23 deal with what to do about foam in your house.