I'm old enough to remember when we had proper winters so to me winter climbing is (or rather was) all about climbing snow and ice, not torquing and scratching my way up summer rock climbs whenever there's a bit of frozen turf. But, given that that seems to be the modern trend then you're perfectly correct - but how often does Engineers Slabs come into condition?
Engineers slabs, and I would imagine most of the other mixed climbs on the N face of great gable was in good condition for at least a month during the last winter.
In addition, lots of the easier mixed routes follow vegetated chimneys, much like lots of mixed climbs in scotland always have done.
That said, the winters have been poorer recently, wish I was a bit older too!
Great Gable actually has a large selection of winter mixed climbs on the north face including some of the hardest in the district - see the winter climbing guide for details
You might just want to add a note to reflect the annual remembrance day service held on the summit of Great Gable at 11.00 on the Sunday nearest the 11th November. I attended this last week along with between five hundred and a thousand other walkers. Quite a different experience. Two minutes silence was impecably followed with only the dogs making the odd yap. The service was initally to commemorate the loss of local climbers from teh first world war. Two local landowners gave a chunk of land incorporating GG to the local climbing club as a memorial to lost comrades. Then in 1923 the land opassed to the ownership of the National Trust.
I hope this helps.
New FRCC guidebook was published this year (2007) for Great Gable and Pillar. Lot's of new photo topos.