Salary Continuance For Severance

A bit of context. Currently on LTD and my employer will proceed with frustration of contract. I will most likely receive a statutory severance package that will be clawed back (almost completely) if I decide on a lump sum payment. Because of this I will ask my employer to see if they are willing to pay my severance by salary continuance. My LTD provider allows me to make a bit of extra income (from other sources) without penalty.

I'm wondering if the length of salary continuance is negotiable and if employers are willing to agree with something long term -- over 2 or 3 years?