Cindy, months ago, after I said I thought I knew why my bedroom ceiling collapsed, you asked why. I apologize for taking so long to answer. I'm glad you're still reading.
In 1983, when I first got this townhouse, built in 1979, in the attic the first owner had put fiberglass insulation, on top of the rock wool the builder used. I went him one better, by installing a floor in the center (I cut 4x8 sheets lengthwise into thirds, pretty much the widest that would go up the hatch from the 2nd floor), and using 16"-wide pieces of plywood to crawl out beyond the center. I didn't know then that when trusses are used to hold up the roof, one should not, iiuc, try to install a floor. I think they bend when you stand on the bottom part. He had spent some time in the attic putting in the insulation but I saw no sagging to any of the 2nd floor ceilings.
I put in much more time, because I also installed over the first 4 years AC power (up through the stack from basement) which I used to put a light in the bedroom ceiling with a second switch next to my bed next to the rear window (a convenience that even the cheapest dollar-a-night hotels in Mexico and Central America had), a light in the ceiling of the small front bedroom I use for an office, a floodlight on the side of the house, and a roof fan (which made the 2nd floor much cooler in the summer even without using the AC. I wasn't used to AC and the first summer I slept in the basement because it was too hot to go upstairs until the next morning. After the fan was installed, it was okay when I got home from work and all weekend. I don't know why so many people on alt.home.repair discounted them, despite my first-hand experience.);
one roll of added fiberglass;
co-ax from the VCR up to the attic and down to the floors below;
a series of two amplified tv antennas and then a full-size outdoor antenna with a separate amplifier;
a sterero speaker jack with wires in the outside wall up to the attic and across to the facing wall (where I hung speakers (one of which was knocked down when the ceding fell);
a phone line because the previous owner had hidden the original phone jack with insulation and another layer of sheetrock (because he was from Louisiana and was always cold in Baltimore). The architect sent me, at no charge, a set of blueprints, and then I learned the phone jacks are not shown on blueprints. Still, I'm glad I have them;
a burglar alarm sensor for my bedroom window (which I could never get to work. I wanted to be able to leave the window open but alarm if someone came up on a ladder and went in. I used a dual sensor, IR and motion in one device, but the wind blowing the curtains kept setting it off. In the end, I've left the window open all summer for 41 years and no one has ever climbed in.
a set of speakers from a 1930's console record player, over the bathtub, that plugs into the tv on the counter, with a volume control in the wall next to the tub. I think I had to remove a resistor from the earphone jack for it to work well, but when I replaced the 14" tube tv with a transistor tv, it didn't have enough power for the 10 or 12" woofer. The replacement tv has much inferior speakers compared to the 30's speakers but does have a remote;
a phone jack in the bathroom, with a piezo ringer, a switch to turn that off and a neon light for when it's off, and a switch to answer the phone, to be used not with a whole phone but with a rewired handset (putting the speaker and microphone in series, like the first phones were.);
a phone jack in the far corner of my bedroom, where I plugged in a neon light designed for phones, so I'd know if the phone was ringing even when the bell was off;
Lights over the mirrors in the bathrooms;
Years after all this crawling around the attic, about 20 years ago I noticed that, although the front two bedroom ceilings seem undamaged, the ceiling light in my bedroom would cast a less than 1-inch shadow on the far walls, from the sheetrock sagging in between. The shadows didn't get any worse for 20 years, and I thought I was safe, but I guess the nails were thinking about doing something. (In 1979 and for a while afterwards, sheetroock was attached with nails, even for ceilings. Now ceilings are done with screws, at least by competent people.) Anyhow I think I was ultimately responsible for the ceiling falling down. You live and you learn.
I had planned to put a heavy white tarp in place of the ceiling -- I had even bought it and was up there with an electric stapler and scissors (to trim around the trusses) and a hardhat (so the nails holding the shingles wouldn't cut my head) -- but when I was in the attic, looking down on my bed and other things far less cushiony, wondering if I could catch myself if I fell between the trusses (and I know the answer is No), I didn't have enough nerve. (I still think the odds are 75% I could have done a good job, but that's not nearly good enough.) When spring comes I'll work on it some more. Or maybe I'll just not use that room for 6 months out of the year. I'll consider that room my summer, vacation home. I can mention my summer home at cocktail parties.
I'm 78 yo, and a friend of mine tells me I'll have to move to a retirement home soon anyhow, so I'll let the flipper fix the ceiling. ;-)