I would recommend using GateTen. They sell parking passes through the Events listing, usually under Miscellaneous tab, in May when events go live. They have 24 hour security at each lot. They have a 24 hour shuttle that runs from each lot to the ICC. Last year a 5 day pass was $74 total. They do have shorter and longer parking passes at different prices. The shuttle is pretty reliable to get you from the lot to the ICC in about 15 minutes or so but it's dependent on traffic. They tend to run every 15 to 20 minutes from the big rush in the morning around 7am to at night, after 7pm. After that you may have to call them to tell them you need the shuttle but they'll be there right away. The shuttles can get crowded in the mornings and on Sunday at convention close, but during the day it's typically not hard to get on right away. And if you don't, there'll be another in a few minutes.
I think you may misunderstand my desire for parking.
I don't want to shuttle into downtown from another campus, I want to have a downtown hotel and not pay $45 a day for parking. If I'm lucky enough to get downtown it would be great if Wed to Mon wasn't the same as a night at the hotel. I don't plan to use my car after I arrive on Wed until I leave on Mon, assuming I get a downtown hotel.
edit: oooohhh okay okay I get it. This isn't the 'shuttle service' of gencon past this is just a strange way of offering parking 'near' the event but not really next to it.
I'm more curious about the lots that are within a block or two and not affiliated with this program.