Here's an example of what can happen if you ignore dark colored, ringed-shaped and/or a splattered brownish pattern on the surfaces of your ceiling or walls:
A MAJOR HOLE TO REPAIR!
This client originally had a stain on her living room ceiling and a section of wall that connected to the stain. Over the years she had two different roofing contractors take their hands to repairing the problem, but the stain became worse. She'd given up on dealing with it since she'd grown used to seeing it, and it just became a part of her home. Like a cough or a cold that doesn't really go away but becomes part of your normal way of living.
I come along to do other corrective painting work in her house - some cracks and window sashes that have lost their protective paint surfaces altogether - and I mention that the stain in the living room looks pretty heinous. She agrees but has decided that now it's gone so long that she's afraid to deal with it for fear of the cost of repair. I explain to her that the cost will ONLY INCREASE the longer she waits, but we skip it as one of my projects this round.
Soon after I've repaired and repainted the other projects, the client decides to get her home refinanced. This will require an inspection by an appraiser. NOW she becomes very interested in having the stain dealt with (it's November in the bay area mind you), and asks me to please repair and repaint that nasty section. I remind her that any repairs I do will likely fall apart if the roof isn't dealt with because whatever has caused the stain to grow larger (rain!) will return now this wintery season. She succumbs to the obvious and gets someone to investigate the roof issue and take care of it once and for all. A roofer comes out, does his repair and she plans this so that I will IMMEDIATELY follow up after his work. I warn her that this is not a good idea as we should wait to see if his repairs have held under fire of the next heavy rains. She wants it done NOW though.
I go in one day after the roofer's done his work and one night after we've had medium rainfall. I inspect - then begin - to scrape and prime the surfaces that are affected with the staining. All seems dry. I do an initial filling of the scraped, dipped-in surface of the long-ruined sections of sheetrock and walk away for an hour to allow the fill to dry. I planned on returning to the repair-in-progress so that I could place another coat of filler (hot mud) to complete the repair prior to another application of primer.
During that hour that I was waiting for my repair to dry, we had very hard rains hit the area. What I found when I returned in that passed hour was my filler sagging and rain-wet surfaces on the ceiling and wall. The roofer had not fixed the problem and now I had to scrape away not only my recent work, but dig out ALL wet materials to allow this one hole from the roof to freely let rainwater come through to the 5 gallon bucket I set up to catch it.
My client had to call off the appraiser and is now having to pay me to do the job that could have been done in the first place after a complete inspection of roof repairs would have passed muster. Now the cost of this ill-fated process WILL cost her more in the long run.
THE LESSON? Listen to the person who is doing the finish work AFTER the work of others is supposed to be completed. This is true for the contractor-client relationship issue I raise in my website as well. Final paint colors AND painting work are the most successful AFTER all the elements have gone in (counters, flooring, cabinets, lighting, etc.) In this case of the stained ceiling, the roofer was like the kitchen remodeler.....everything should be tested and dry before applying the finished paint!