outside lights dont work properly
My first thought is that the sensor has debris on the outside, or - if there is a protective cover on the sensor - has built up a film on the inside of the cover.  Try cleaning it well outside, then see if you can remove the cover to clean the back side.

My 2nd thought is that I've often found finicky electrical problems to be caused by a loose wire or bad solder joint.  You might turn off the power, open the case up, and look for loose/broken wiring or cracked solder joints on the circuit board.  This would fit with your description of the problem - they quit working after they have run for a while, and don't reset until the next day (when they would be cooled off).  It's not uncommon for an electrical device to quit working when it gets "warmed up".

Last thought - I've worked with quality assurance in my career- It's pretty common that the business folks decided to go with a cheaper material and warranty the product for only a year or sometimes 90 days.  They count on no one returning the product and they make a bigger profit.  If your lights were on the low end of the cost spectrum, it might be more beneficial to just upgrade. :)