Generally speaking, they are expected to last between 10 and 25 years. This largely depends on the manufacturer, the quality of materials, the frequency of use, and the maintenance. Most portable solar panels will see a gradual decline in efficiency after 10 to 15 years of efficient operation.
[pdf] Charging below 32°F (0°C) can harm the battery and shorten its life. For winter storage, disconnect the batteries, charge them to 50%, and store them in a dry, well-ventilated place..
Charging below 32°F (0°C) can harm the battery and shorten its life. For winter storage, disconnect the batteries, charge them to 50%, and store them in a dry, well-ventilated place..
When not in use, experts recommend storing lithium batteries within a temperature range of -20°C to 25°C (-4°F to 77°F).
[pdf] 
