Re: should i keep doing this?
You will need to do what you feel most comfortable with. Were it me, I would try to always get food out there, at least every other day or so. I do not think it is fair to provide a source of food that they count on and then remove it when they need it most, in the winter. I know you are proposing to 'wean' them now, but I just don't feel that is fair and you have a good chance of them not surviving through a NY winter w/out a food source.
If *you* think you can't make it through snow, how is a small kitty supposed to do so *and* find their own food source? I don't know. Perhaps the feral cats of the Northern climes have figured something out, but it is my belief that once an animal grows to depend upon us for something, we need to continue to provide it.
That is only my opinion, feeling, whatever ... and you still need to do what you can, and if you cannot provide food all winter, well, then you simply can't. I just don't have any suggestions that would be helpful for you in this situation. Good luck,