Hi Tim!
Are you coming from USA just to do Aconcagua? What kind of acclimatization routes do you have planned? Are you carrying all your equipment or using mules to Baseceamp then porters? How much weight will your backpack have?
The last couple years on Aconcagua have had complicated weather. I climbed this January and also have a couple friends who work as guides there and said it's been a trend. We used mules to basecamp (100% recommended ) and then carried all our own weight from there.
The issue is from start to Plaza de Mulas, it's over 20miles/38km. Not kidding, even if you use mules and carry a smaller backpack, it's not a good idea to go past Plaza de Mulas (14400ft) on your first day. Plus, my bets are, you won't want to either.
I had to push summit attack back 2 days for bad weather, and also, had white out storms 6 days in a row, which meant we had to open route each morning, which was tough with altitude and the weight. Albeit, going less days, you'll carry less food, but still the weight will be a factor if you're facing snow conditions.
If you've never been over 14000ish, I'd seriously give yourself more time. The people in the tent next me had never been over 18000 and they really had a hard time (and didn't summit). You don't know how your body will react so it's better to be safe than sorry! My partner didn't summit due to altitude issues, and we'd been doing prior acclimatization routes up to 18000ft.
My partner and I went on a long schedule, because we wanted to see all of the park (it's gorgeous!!). That means we took 2 extra days to detour to Plaza Francia, 1 extra to do Cerro Bonete and a rest day since that's what every suggested to us (and I think was very valuable). That said, including 2 bad weather days where we portered stuff to buy time/carry less weight, I summitted day 11 and was out of the park day 13. Here's my schedule which I detailed pretty well:
http://www.findingthenorth.com/aconcagua-normal-route/ If you need to cut it shorter, best scenario would be straight to Plaza de Mulas, give yourself a rest day, then Camp 1, Camp 2, Camp 3, summit/Plaza de Mulas, out. Plus 2 bad weather days/wiggle room if you're tired. If just so highly depends on your weather and snow. I have friends who did it in 7 days (no bad weather) but they were doing acclimatization routes to 20,000ft with 45lb backpacks for about a month leading up.
Also, just as a note, it's a gorgeous park and if you can take a little bit more time, do it. If you give yourself the time, you should be able to summit... and your eyes and camera will be grateful too
Let me know any other questions, happy to help!!
Chelsey