I don't have a solar powered, but do have a post light out front. Mine has provisions for a "dawn/dusk" sensor to turn it on and off automatically (when the switch in the house is left on), but having been forced to replace the sensor at about 2-3 year intervals (due mainly to dusty ambient and occasional "bird s**t strikes") I finally just cut the sensor out of the circuit.

Since all the solar lights I've seen use a similar photocell sensor, asking around, perhaps at local garden shops, might give you an idea whether you have similar conditions that might tend to limited sensor life. With smaller marker lights, you might have to replace the whole fixture to restore sensing, but I'd expect the sensor to be separately replaceable in a post light(?).

All solar powered devices require rechargeable batteries, of course. Larger units - which are available for "stock tank lights" and such in farm country - generally use wet cell 12 volt batteries. In solar use these may have fairly short life. You may or may not get better life out of premium, deep cycle, gell cell, etc., batteries. Most stockmen I know consider it about an even tradeoff to use the cheapest (motorcycle) batteries and replace more often. I wouldn't expect that you'd want a light big enough to need a battery of this kind, but it could be info usefully tucked away just in case. Some fairly large units are available fairly cheaply - if you can handle "ugly."

Most smaller lights, and probably ones of the size you'd want, seem to use AA size NiMH or Li-Ion rechargeables. Really cheap ones may not have easily replaceable batteries, although decent quality ones should be replaceable. All of the common kinds of smaller batteries should be brought to full charge prior to beginning any discharge cycles, so at first installation - or when replacing - it would probably be good practice to put the rechargeables in a charger and charge for a full day before returning them to the light/panel fixture for the first turn-on. At the least, the first "turnon" should be early in the day so that a full day of charging can get done before the light comes on. (but RTFM for the ones you get?)

As open mike comments, short days in winter may not get full enough charge for the light to last all night. My Texas stockmen buddies complain about "battery freezing" when the charge cycle doesn't keep them up, but I don't know that low temperatures adversely affect the smaller "dry-cell rechargeables." It might be something to ask, or maybe some one has researched it or has experience and would comment.

Some kinds of "marker lights" and/or "yard lights" cannot be turned off (for some yard lights it's "without calling "a light guy" to turn them back on"). Some inexpensive lights may not have a switch. Consider whether this is a needed feature. There might also be occasions when an "override on" switch would be convenient, but I don't see mention of one in specs for the few units I took a quick look at. (Can you tell if the thing's working in daylight when you can fix it?)

Consider security. Anything that "looks exotic" - especially in an exposed location - may be subject to unexpected theft, pilfering, or vandalism. The visible presence of a solar panel in an exposed location might be enough to tempt someone to commit "irrational acts."

John