Permanent Residant Requirement Extension?

[RKartman]

I am a US Citizen and permanent resident of Canada (since 1972) and have been recently expanding our Toronto business into the US. I am aware that I am able to be out of the country for a cumulative 3 years per 5-year period, but I am concerned that my future plans will use up the 3rd year limit very quickly. Is there any way to apply for some sort of exception or extension?

Thanks,

Ron