I've riden in the Chilcotin's for almost 20 years. The key to remember is just enjoy the experience. It takes a few trips to dial in what is needed to take.
Some nice loops are Tyaughton lake ride up to Taylor basin, High trail to Windy pass and then down to Spruce lake. Then ride out Gun creek back to Tyaughton lake. Best time was around 6 hours and that hoofing it. Only pushed a very short distance up past the old mine site. I'd count on 8 hours for most fit riders.
The ride up Gun creek from Jewel bridge to Spruce is always nice. Take the high trail to Spruce a better route then sticking to Gun and then pushing all the way to Spruce.
Jewel bridge to Deer pass and out Spruce lake to Jewel Bridge is 12 hours and not advised as a day ride. Greg Stoltman can attest to that. He collapsed and slept for a bit while my friends packed up his stuff.
My favorite is to go into Graveyard. Camp there and do some day trips from there. Dil Dil plateau is very nice. I have a picture taken within a few feet of Lee Lau when he went up into that same basin. We hoofed it up to the ridge to ride the Plateau.
There are just so many possibilities and you do not need to use float planes or horses. Just go self contained and you are free to ride anywhere. Three day trips are optimal as well but two day trips can still cover lots of terrain. Don't forget Slim Creek there are some really nice rides further south with very different topologies. Then there is Paradise Valley, Misty Mountain, Big Dog, Shulaps, Yalakom etc. Truax might have something to offer. Did that once back in 92 and never went back. First and only mechanical in the Chilcotins where I taco'd a wheel.
I'd be happy to provide suggestions and might even try for a ride this fall. Looking for willing participants/victims.