I will echo
@spacemt354 comments. There are a lot of variables tied into hosting from size, duration, solo vs team, how much PR type stuff you want to do, extras, etc. Above all, I would say work on a schedule for the entire season, what you want, when you want it, and then just have back up plans in case things go a little off which they can almost assuredly do through no fault of your own.
It may take a little more time then you expect, but it's hard to say. I felt I had a pretty good handle on things, but one area I could have improved on was the timeliness of reviews. I was able to get new challenges, etc out but didn't always get reviews/results out as fast as I wanted or would have liked. Now granted I had a death in the family one week, but some times you just get busy. Just be as prepared as you can.
I think a lot that will be a determining time factor for you as well is how much extra do you want in there? There's no exact right or wrong way to promote or run your comp, but from the better comps I've seen the last few years , there was always something different, or new that helps keep the fun/chatter/involvement going. With the Great Movie Ride, I tried doing a couple preview trailers for the season, a mini challenge each midweek, posting frequently in private team chats if I saw they needed a bump, or on the itself forum itself and did a season ending award show. Not saying you have to do any or all of that, and I'm not 100% sure how it played out with all the contestants as a whole anyway, but you'll want to consider doing something to try and get potential players excited and engaged.
For the host, I feel like it's almost a giant imagineering challenge personally. Look up some of the past comps for topic ideas, how they went, etc. If you are having fun with it, in all likelihood your players will too.
