My experience: the old Datamarine & Raymarine (e.g. ST60 and even older, as well as newer) displays work great and work forever. The sending devices do not. And they aren't the greatest problem.
Speed wheels last me ~10-15 years. The last time one failed I looked at the specs, and it was rated for XX revolutions, which equated (for me) to something like two years' use. Laugh. Obviously they have lasted longer for me.
Wind instruments anecdotally might live five years; many do not. I'm sure others will say theirs is 15 years old; my experience and observation indicates they don't live long. There have been numerous reports of the Raymarine wireless wind devices dying after a year or two, so while wireless is easy, I am apprehensive.
Aside from device failures, my experience is that 90% of failures are in the wiring. This applies to both connectors and direct-wire. The wires flex over time, and break. I'd happily spend the cash to replace a failed display, but that's never my problem- it's the cabling which has to be pulled out and replaced. With pre-attached connectors, often the connector end(s) has to be run through holes (e.g., bulkheads, pedestal tubes, pods) meaning the connector has to be cut off, wire run, the connector is re-attached, a real PITA.
I'd stay away from any used speed/wind electronics except displays, and maybe depth transducer. There is no cheap way to do what you want, except what Don L said. If you're not racing, you don't need wind speed or direction, and anyone with any experience can use their face and Mark I eyeball. Windexes are inexpensive, low-tech, and easy to install, go that route for wind direction indicator.