I've been legally separated for more than 20 years because my divorce case is so complicated & a divorce would be too costly.

Sorry no divorce case is that complicated Esp after 20 years, by this point, all the kids are over 20 so there is no custody issues, at this point all property would have been divided by use.

I can not see any reason for much issue after 20 years

I'm in NY - what is so complicated? Your Separation Agreement addresses all of the issues and you file for divorce using that SA as the grounds. The terms of the SA turn into the terms of the divorce. That includes custody, support, all financial issues. If the SA is outdated (for whatever reason) you should enter into another agreement. Likewise, if a change in the law changes your SA it is no longer valid if you now use it as a basis for a divorce.

I'm also in NY - and I'm familiar with Oswego.

Anyway, what is the complication?