I have a Casio 2688 atomic watch and lately it does not hold a charge for a long period of time. It will recharge and then quit within a day.It will hold a medium charge for about 24 hours at most, but never a high charge. Would replacing the help?battery

I wouldn't use a "standard lithium battery", because the CTL 1616 is a special device. It has a different voltage (2.3 V instead of 3 V) and consists of different materials.
It's not really a battery, but a "capacitor", which means, that it's mainly supplied by the energy of the light. The capacitor is designed to maintain the functions only for (short) periods of darkness. Unfortunately, the capacitor loses its ability to store the energy over the time. So your watch may be able to maintain all the functions for more than 11 months of darkness in the BEGINNING, but after a few years it may only last for a few hours!
However this may be strongly influenced by the use of the functions: for example the automatic reception of radio signals or using a digital compass may strain the energy seriously.
So, inserting a new CTL 1616 should be the best, and maybe thinking over using the different functions could make the capacitor last very much longer. I wouldn't use a "standard lithium battery", because the CTL 1616 is a special device. It has a different voltage (2.3 V instead of 3 V) and consists of different materials. It's not really a battery, but a "capacitor", which means, that it's mainly supplied by the energy of the light. The capacitor is designed to maintain the functions only for (short) periods of darkness. Unfortunately, the capacitor loses its ability to store the energy over the time. So your watch may be able to maintain all the functions for more than 11 months of darkness in the BEGINNING, but after a few years it may only last for a few hours! However this may be strongly influenced by the use of the functions: for example the automatic reception of radio signals or using a digital compass may strain the energy seriously. So, inserting a new CTL 1616 should be the best, and maybe thinking over using the different functions could make the capacitor last very much longer.