Booting from an SSD is the right answer for anything running continuously, and it is not only about failure rate.
What you get:
Far more write endurance and proper wear levelling, so ordinary logging stops being a countdown.
Much better random performance, which is what actually makes these boards feel slow. Databases and package updates in particular are transformed.
Better failure behaviour. SSDs tend to degrade in ways you can see coming through their health reporting, rather than dying silently.
Practical notes:
Check your board can boot from USB or has an NVMe option, and update the firmware first if needed.
Power matters more with an SSD attached. A drive drawing from the board's USB is a real load, and an underpowered setup that was stable before can start browning out. Use a good supply, and a powered enclosure if in doubt.
Not all USB enclosures behave. Some controllers are unreliable on these boards. Check what people report for the specific enclosure before buying.
And keep the card habit that matters regardless: a known-good image and your configuration backed up somewhere else. An SSD makes reflashing rare rather than impossible.