sounds like a nice long summer hike. in terms of mileage, i'd say that for a normal lightweight/UL backpacker, 25-30 mpd on the Colorado Trail is tough. i did the first 360-370 miles of it last summer in 14 days, and it was HARD. about 27 miles a day, a couple fewer in the beginning and up to 33 one day. i have fair experience hiking distances, and my partner on the trail was a triple-crowner, and we both felt it was a serious project to do 27+ a day. we only had 19 days for the whole thing, so it was definitely testing my limits for day after day long distance. i think the lack of rest days, even with just reduced mileage (e.g. 15 mpd) - let alone a day off - was hard on the body after a week or more. (my training for the hike could've been better, but that's always the case.)
in the interest of full disclosure, i, like some other people i know, was fairly to pretty disappointed by the CT when viewed solely as a "thru-hiking" trail. TONS of road walking and LOTS of going up 4,000 feet just to go down 3000 feet on the other side of the ridge. though thunderstorms up high can be dangerous, i would've liked a trail that got up higher and stayed up a bit more. (we got chased off snow mesa, of course, by a crazy thunderstorm.) in terms of a thru-hiking trail, it really feels like what it essentially is - a cobbled together stretch of existing trails, 14ers access routes, old logging roads, old other roads, and current roads. i forget the actual value, but i think it's something like 40% roadwalking (old and new roads). i guess i am partly spoiled by the pct and hikes in the high sierra and other higher elevation areas in the west. spending an entire day walking in the forest on a logging/atv road just isn't my cup o' tea - especially since you know that 500' off the ridge to either side is amazing scenery, and you are following the road up the middle of the ridge in the forest. where an engineer would put a road and where a trail maker would site a (purpose-built) trail can be close, but a world apart, sometimes.
that said, there were some crazy beautiful stretches, and amazing scenery. and we actually bailed before the "best part" - the san juans, so i can't speak to that amazing section. and don't miss the on-trail hot springs resort... pure heaven. if you have time (we didn't), try to bag a couple 14ers.
if you are interested, i could share our itinerary with you. let me know. not sure about your resupply plan - we actually had three ON-TRAIL resupplies (we bailed at the third one), so hitching into town will also take additional time in the schedule. the leadville hostel rocks.