I've seen hundreds of machines and timing being off isn't something I've seen unless it was caused by something other than timing. I've made a machine go out of time by doing stupid things but they don't just wear out and go out of timing for no reason that I have yet seen. I had a machine with a bent needle bar be out of timing but it was because it was a bent needle bar not because it was out of timing. I've had a loose shuttle because I loosened it. Sewing over a pin with an old black machine might make a nick in the hook from the needle being bent and forced but I doubt if it will go out of timing and even then I think it takes a lot of stupidity to get a burr. If you are trying to sew through heavy fabric you will need a needle made to do that. If the needle isn't enough you may need an industrial machine and even then some are not made for heavy fabrics. I have an old worn beater Singer 15-75 that sews through amazing amounts of fabric. The worst case I can imagine with that machine would more likely be a bent needlebar from weight or pulling stuck fabric than for that machine to go out of timing.