What's the mileage on the oil? Me being me, I'd forgo the "oil is cheap" train of though, although completely valid, I like to see cold hard facts. I'd pull a sample when you would normally change it in the spring and send it in. If it makes you warm and fuzzy, or you don't have the tools to do so, change the oil at the same time. With those results, next year at this time you can be confident that the winter was/wasn't that hard on the oil and I do/don't need to change it in the spring with over 50% life left on the OLM. Time has no effect on the oil IMHO, however personally I wouldn't go over a year.
With a good quality full synthetic oil and premium filter, I'd have no problems taking the OLM right to 0%. Back it up with a couple of UOA'S while doing so and maybe one every year or two to make sure nothing is changing in the health of the engine.
Alternatively, you could short change the winter OCI and leg out the summer OCI'S. That would be a pretty safe bet as well.
Sure it's cheaper to just change it, but I like to know for sure.