My grandfather used to say a watch tells you when it wants help, and people mostly do not listen because listening costs money. He was right about the first part.
Below are the five things customers describe to me most often, and what each one usually turns out to be. Four of the five are repairs. One of them, sometimes, is not.
1. It runs, but the timekeeping has drifted
Your watch used to be within twenty seconds a week and now it is two minutes a day. Nothing dramatic happened. It just slid.
That is almost always old lubricant and a movement that wants a service, not a replacement. On a mechanical watch it is the single most common thing across my bench, and the repair is routine. A watch that has drifted is telling you it is still healthy enough to be worth saving. Ignore it for another three years and that stops being true.
2. The power reserve has collapsed
You take it off Friday evening and by Saturday lunchtime it has stopped, when it used to run through the weekend without complaint.
Usually a tired mainspring, sometimes friction that has crept into the going train. Both are ordinary work. Neither is a reason to buy a new watch.
3. Something feels wrong when you wind or set it
Grinding. A crown that will not screw down cleanly. A stem that pops out. A crown that spins freely without doing anything.
Stop winding it. Genuinely, stop. A stripped keyless works will chew through parts that are harder to source than the ones already broken, and I have seen a five-dollar fix turn into a three-hundred-dollar one over a weekend of somebody trying to make it catch.
4. Moisture inside the crystal
Even a faint haze that clears by afternoon. Even once.
Water is in there, and it does not evaporate out of a sealed case. It sits on steel. Bring it in the same week, because at that stage it is usually a clean, new gaskets and a pressure test. Leave it a month and we are talking about rust on parts I may not be able to replace.
5. The case is beaten up but the movement is fine
Here is the one that is sometimes not worth repairing, and I will tell you so.
If the case is a plated base metal that has worn through, the crystal is a shape nobody makes anymore, and the movement is a mass-produced quartz from the nineties, then the honest arithmetic does not favor the repair. I can do it. It will cost more than the watch is worth and more than a comparable used one.
The exception, and it is a big one, is if the watch belonged to somebody. Sentiment is a perfectly good reason to spend money on a repair and I would never argue a customer out of it. I just want you making that decision with the numbers in front of you rather than after the invoice.
The general rule
Anything mechanical is almost always worth repairing. The movement is the expensive part, and it is the part that lasts. Cases wear, crystals scratch, straps rot, and all of that is replaceable.
What tips a watch into not-worth-it is a movement that cannot be sourced or a case that cannot be made whole. Everything else is a question of what you want to spend.
Bring it in and I will tell you which one you have. Looking at it costs nothing, and I would rather turn away a repair than take money for something you are going to regret.