Many of the solar/handcrank flashlights out there use cheap coin cells to store energy, and so don't last long at all -- the coin cells can only be recharged so many times before they won't take a charge again.

Good ones use capacitors. Capacitors have a much longer service life but may have more parasitic drain. Good ones can also use other battery technologies like lithium-ion, although batteries that are allowed to fully discharge may be damaged or destroyed.

Given where the your unit is sold and that it comes with a five year warranty, I would think that it is also capacitor-powered.

The only ones I have in active service are powered by capacitors. One is a solar/handcrank radio/flashlight gizmo from Eton, the Microlink FR160. It lives in our designated tornado shelter and has given us flawless service. Your post reminded me to test it and set it on the windowsill for a solar charge. This unit has a USB output for charging a cellphone; I would guess that you'd need to crank it for a solid ten minutes to get a useful amount of charge for a smartphone. Highly recommended and available online for $19. I have no affiliation with Eton.

The other one I have is a no-name handcrank LED flashlight with a 12V output. It's chunky but light and surprisingly sturdy. After banging around in the trunk of my car for ten years it still works.

I haven't seen one that performs worth a darn compared to modern battery-powered LED flashlights. Solar/handcrank flashlights are significantly larger than many battery powered flashlights. For me, I wouldn't put one in a kit that was going to be carried by a person any significant distance. For a kit that sits in a vehicle or a structure, they can make sense as a backup.