I don't know how severe your winter will be but leeks are very hardy. It is standard practice to sow them in a seed bed and then transplant as you eventually did. It is true they will flower next year but depending on your weather it might not be very early so you could still possible eat them next year. However the flower stem starts to develop long before you can see it and sometimes you will find a fibrous stem inside an innocent-looking leek.

It isn't necessarily a good thing to have 2 - 3 inches diameter, especially if they have developed slowly. The outer leaves can become thick and tough. Pencil thin leeks are absolutely delicious. Check out Leeks Vinaigrette.

I plant a lot of leeks, and if we don't eat them all before they get buried in snow, I mulch them well and we eat them in early spring, as soon as I can dig them. So you can harvest and eat them now, or harvest them first thing in the spring, but they won't gain any size between now and then IME, between shorter days and cold temperatures. If you wait too long to harvest in spring, they will go to seed, and they get woody IME. I mulch them as far up the stalk as possible, though that is sometimes limited by the amount of available mulch, since any parts that freeze will be mushy come spring. In general, I don't find that for the varieties I have grown (King Richard and Lancelot) that the large ones are any less tender. It may have to do with how I cook them or the variety. We enjoy having the early season fresh veggies. Some varieties weather the winter better than others.

This far north (and probably in your area as well) leeks are usually seeded in flats under lights and then transplanted outdoors, or bought as small plants and transferred to the garden. Our growing season isn't long enough to develop really good size otherwise. Our leek sets are always started in late February, well before any other crop for which we start seedlings under lights. The last few years I have bought my leek starts, and that has worked well also.

I'd say eat some now, mulch and eat through the winter whenever you can dig them, finish eating by very early spring.

Here is my schedule for leeks (also zone 5b):

plant indoors in pots in January or February.

transplant outdoors in April. This is done by making a dibble hole in ground with a screw driver and lowering the baby leek into the hole as deep as you can get it. Then water -- do not pack soil around to fill the hole, just let rain and watering do that eventually.

mulch in late fall and also cover with fleece if your area gets really cold.

Eat November through March.

Just made potato leek soup last night. Enjoy your leeks!

Thanks for all the responses. I think I will pull most of them over the next week or so and then see what happens come Spring. I did just buy some T5 lights so I'll get next year's leeks started in January. Should make it easier to appropriately space in the garden.

I agree that they may become somewhat inedible if left too long. The central stem seems to grow thicker and higher up in the plant if left too long at the expense of the tender part. I also start my first early leeks (King Richard) around new years day and plant out towards the end of March. This year I am trying to spread out the harvest more by staggering the planting and using some different DTM varieties. I have seeds for American flag (110 DTM) and plan to order some Bandit (120 DTM) from Johnny's that are supposed to be very winter hardy. I will start seed for both of these in late February or early March and plant out in early June. I transplant into 6" deep trenches along the edge of my raised beds and fill in the trench as the grow.

Yay, only 10 days to go until starting seeds! We really like leeks in Chinese dishes like Mongolian Beef or chicken.