The only real maintenance is to ensure that the solar panel is kept clean - you should wipe the solar panels regularly, maybe once every two weeks. Also, you might need to cut down plants if they stat growing over it and and  blocking the sun.

I would simply say check them every now and again to ensure the lights have not fallen over, and also wipe away any stuff on the light and specially the panel with a clean, damp cloth.

If your solar lights have been outside for a while, then you might have noticed that their plastic components aren’t as pristine as they were. In fact, they may now be a yellowish color, making them visually unappealing.

I found out that this is due to a process called oxidation which is common for plastic exposed to the elements such as my plastic garden solar lights. I also found out that not only are they unsightly, they can also compromise the structural integrity of the lights, greatly shortening their lifespan.

The answer is yes. Many homeowners can tidy up their solar panels at least once a month to ensure optimal function or performance.
If you currently reside in a dry but not barren region, the solar panels will be fine with cleaning them every six months. You can do the same if you reside in a location where there is a tropical climate.
It is important to regularly monitor your solar lights and gently clean them when they have accumulated a layer of dust, dirt, and residues.