I rode it last month from Troutbeck to Kentmere. It’s got loose gravel all over it now, which made the climb almost impossible in places – the gradient wasn’t the problem, it was the lack of traction. The descent into Kentmere used to be quite challenging with lumpy rocks in places; now the challenge is to stay upright on all the loose gravel and stones which encourage high speeds but aren’t actually much fun to ride on 🙁
Last time I was up (which was quite a few months back), it had been sanitised on the troutbeck side. This often gets done and it almost never survives a winter.
It’s still a tough climb, and traction is an issue as mentioned above. Not as good as it used to be. I need to drop to a 22T ring so I think if you’ve only a middle you maybe walking sections, although you might well be stronger than me (which isn’t difficult).
Anyway, I’d imagine the route you describe would be 2 hours.