I look at the issue from a dietary perspective. changed to a seasonal diet and then keep lengthening the seasons at either end as and when. A bit of a faff sometimes, but not really, and gives me valuable weeks of food in the 2 month "gap".
Stored root veg, either in the ground or sand easily last til February, and a late winter holiday crop of potatoes in the greenhouse border help this, as December/January usually sees some of the stored Summer crop sprouting.
Being as I don't eat animals, the collection of beans and pulses in a dry state is very important, and like squirrels, I regard dried beans/nuts/ seeds as "fresh". And talking of squirrels, a bit of late Summer foraging for hazel nuts helps too. That counts, doesn't it ?
An early crop of broad beans is essential in my regime to bridge the gap, hence over Winter planting, along with peas and carrots in the greenhouse to start harvesting end of April.
Red cabbage are useful as they last for months in the fridge. PSB is an absolute must and start just as the Brussels are finishing. The kale is an ever present. Various hardy greenhouse greens also supplement.
Japanese onions and leeks are useful to take over when the stored Summer ones are finished, although this year my leeks weren't great. Have put in twice as many senshyu to compensate, and put them in early. Half will be used small or spring onion-like when I run out.
I must be doing something right as I probably spend no more than £30 a year on vegetables, and that's mostly Winter treat peppers/cauli etc when friends and family come around. All I buy in shops are dairy, flour, grains and biscuits...... oh, and chocolate. Not much I can do about that as I don't have the room to grow grain, although I keep threatening to do so. Seems like a lot of work though harvesting and milling anything useful.
Tomatoes and fruit are frozen, and in my opinion redcurrants are better out of the freezer than fresh. I still can't keep apples well all Winter, so lots of them get frozen too. Must get into pickling more.