How long to get used to new food?

I was feeding my cats Nutro Max Chicken formula dry. We ran into financial troubles, for the past almost month and a half. I've not been online because we have had no cable/internet to get back on our feet etc.
Anyway... I decided we would go to a less expensive bag of cat food for our 4 kitties, for Nutro Max Chicken at our local Pet Store when its not on Sale its 29.99, for the 20lb bag, at another local Pet Store Chicken Soup for Cats Adult Formula is 18.99 for the same size bag. A considerable savings, I've heard great things about the food on this site, so I figured I'd make the switch & help us out in return & still give our kitties a GOOD diet.
I thought I still had a little under half a bag of the OLD food left in the box ( I pour the food into another container that I dispense from & the bag stays in a big rubbermaid box ) & when I went to get more out of the box I found that I had only enough to transition them for maybe 3 days.

Not long enough for the New food NOT to upset their tummies, needless to say I have quite FOUL litterbox odors for the past week

Plus when the kitties sit on my lap... *gah* they smell like 'butt'

I HAVE noticed they have wonderfully soft fur... other than that... PU... lol.

So, without haveing the nice transition... how long will it take for their tummies to transition?

It'll do no good to get even a small bag of the old food now to mix in now would it? They've already been on the new food for a week... so I just have to wait it out at this point right?... just for how long... bleh... I mean... I generally scoop my litterboxes 2x's a day before... but NOW I'm doing it like every time they USE them....

Thank you for any insight you can offer.

you went from a two or three meat and two grain food to a five meat 6ish( some may be grain likes )grain... ie not to rich to quite rich...

give it another week or two if you can

I bought a bunch of Chicken Soup wet for my cats (both adult and kitten formulas) and their poo just stunk way too much when they ate it for me to keep using it. It was so bad that I decided to donate what I had left to the Humane Society. I don't know if the dry is anything like the wet though, but after posting about it here on TCS I got some responses from people who said they had the same experience with Chicken Soup.

Just an update on this... as an FYI for anyone doing research on Chicken Soup... I gave it another week and a half from the post & *bleh* scooping 10x's a day & having cats that smelled like butt was not my 'bag' I went to my local pet super store & they had The Cat's old food Nutro Max Chicken on sale for 19.99 for the 20 lb bag & I bought it & "transitioned" the cats back on their OLD food which they were HAPPY to do, because they were not eating the Chicken Soup so well, my cats were NOT the type to leave food in the bowl all day & they'd just pick at that stuff.

I noticed right away once they were back on their Nutro Max Chicken, that their stools were solid, that litter box odor was back to practically nothing & my cats no longer smell (because they did not have icky poo's)

Even buying Bags of their Old food not on sale, when its 26.99 or 29.99 or whatever the regular price is for the 20 lb bag, is WELL worth the extra money paid rather than the headache from the few bux off with the Chicken Soup, with MY cats anyway... seems they could not handle the richness of the food.

Anyway, just wanted to update on this as info for anyone doing reserch on the topic.

My cats have stomachs of steel, I switch food on them all the time frequently without warning and have no problems. My cats did fine on Chicken Soup, but the dogs got horrible gas and where very itchy so dropped that one out of my rotation for everyone.