So I'm 2 days post my first IM, and already thinking/talking about my next one with a friend who did one a couple of years ago. At this stage I'm thinking about one in around 14 months time. I'd like some help/advice with how I structure my training on a macro level, not so much about the detail of the sessions as I think I can manage that, but more about what focus blocks I put where.

My race a couple of days ago had a swim of 1:12 (I think I'm 5-7 min quicker I'm better conditions), bike of 5:43 on AP of 168w (again tough wind with 1,500m elevation gain), and run of 3.55. Ideally I'd like to go closer to an hour for the swim (so take around 5-7 min off my current swim ability), bike with an AP of 200w and run 3.30. I think on a slightly easier course with normal conditions this should put me comfortably under 10 hours. Is this achievable?

I'm not that big a fan of riding much through the winter, so was thinking about doing a run/swim focus from basically April - September then bringing the bike back through spring/summer, and combining them all for a IM build of about 10 weeks in Autumn.

My main questions are, how should I structure the focus blocks and for how long so that I can at least maintain the areas not in focus. Particularly when I bring the bike back in, how do I hold on to the gains I've made on my run and swim?