Hmm. What kind of pipe is it? Some pipes are dipped and will get some stain inside the bowl. After about 4 or 5 bowls it will burn off and the taste will be gone. Alcohol cleaning will help a little with that, but you really have to smoke it out.
Everyone's cleaning cycle is different, but After smoking I just run a cleaner or 2 through the stem and shank, swab out the bowl and let it rest 1 day for each bowl I've smoked that day. I only do what I call a "deep clean" with alcohol every couple of months, because I rotate and only smoke 1-2 bowls a day.
I can smell when they are sour as opposed to sweet so I go more by that than actual time.