Yes, I run a weekly long run and at least one or two other runs during the week when I'm not training for a marathon. I love Cathe's cardio and miss them when I have to cut back on them. I'm happy to be able to work a few in now! I live on the central coast of California where the weather is almost the same year round so I don't have the ice, snow and wind issues that you have so running is hardly ever a problem!
(Side note of no relevance: I just finished reading Devil In The White City which was a great story about the Chicago World's Fair in 1893. I've always wanted to visit Chicago but after reading that book, now more than ever.)
If you maintain a weekly long run base you'll be ready to run any 1/2 marathon that comes along during the year and when you begin training for the next full marathon you won't really have to start increasing your mileage until about 3 months out from the event. So it won't be a long 6 months where that is the main focus. Plus you've got the endurance base now so can concentrate on speed more during the week while running an easier pace long run on the weekend. If you do that speed work during the week you will naturally see your comfortable long run pace getting faster. Hence, a faster, easier (but still hard) marathon next time.
This time I concentrated on the freestyle workouts for lower body about 4 times a week and went with heavy upper body work with about three to four days of core work thrown in. I just used Cathe lower body workouts with 70% of what I can lift heavy. I love the GS upper body workouts and gained a lot of strength and definition. For instance, I am now able to do all 72 pushups on my toes. The core work was a mixture of P90X ab ripper X, Cathe's Core Max and MTV Pilates Mix.
I maintained an even pace for the entire marathon I just ran and finished strong, yet spent, so to me this was success. (even though it wasn't under four hours(I HAVE to get over that!!))
This year I plan on staying with the same weight training but increasng my focus on intervals and tempo runs.
It's very addicting isn't it?