On a more serious note, I think this is one of those questions where the answer is, "it depends". If you are coastal cruising in generally populated areas, aka pretty much all of the US coast line, I would carry minimal spares.
- Under any circumstances I would carry a bunch of racors (or whatever brand you use). You can get a bad batch of fuel anytime. And you can make your own bad batch of fuel anytime by getting caught in rough seas and stirring up settled crud in your tanks.
- Additionally, I'd carry spares for maintenance and wear items. So impellers, belts, and other filters. Also fuses and some basic electrical components (wire ends, etc.) and some misc plumbing parts like misc hose and clamps. Maintenance parts are going to get used within a year anyway, so you know you will use them and you know they won't have time to go bad. So other than space, no really downside to having them.
- Regardless of what maintenance spares are on board, I'd think carefully about what repairs I would realistically do at sea vs getting home via one engine, a wing engine, or a tow. Repairs are much easier at the dock, especially when you discover some gasket or o-ring that you need, tool that you need, or when you break something else on the boat in the process. This is the voice of experience
- Once back at the dock, the only advantage to having spares on board is time. You can use a part that is on-hand, or you can go to a local supplier, or order via mail. But for anything you need to order, you can probably get it next day if you want it badly enough. So having spares on hand saves you a day or so, maybe.
All this suggests carrying minimal spares, thanks to widely available get-home techniques (alternate propulsion or towing), and exceptional mail-order suppliers.
However, things are much different when you start traveling to remote destinations. Even the Bahamas counts as remote, though physically it's not far away. I had a watermaker part sent to me overnight in Hopetown which is a populous location, and it took a week. I hear regular stories of parts simply never arriving because someone somewhere along the way decided they liked the package and kept it for themselves. This is where there is a whole different reason to carry many, many more spares.... time.
If you are in a far away place and something breaks, even something non-critical, repair can be a real logistical nightmare and cause significant delays simply because of parts. You can frequently find a local mechanic or technician, but without parts they cannot help you. Our parts sparing is based on this view point. I look at important systems, what is most likely to fail, and I come up with some action plan in the event of a failure. If there is a long term way to work around it then I might not carry any spares, but more often than not I will. So I have a spare fresh water pump, manual holding tank discharge pumps, spare fans, hydraulic parts, battery chargers, monitors, critical electronics parts, lights, etc. Basically I want to avoid getting stuck somewhere waiting for parts.
Of course any sparing strategy is a gamble, so you are only improving your odds. In reality we all know that the spares you have are the ones you won't need, and the spares you don't have are the ones you will need.