Grandpa30548

It depends on what general condition this tool is in, and how well it performed for me when it was working as to whether or not to fix an old tool.
I own some old Craftsman woodworking tools that are cast iron and bullet proof, and I go to great lengths to keep them maintained and working. New Craftsman (and stuff sold at home improvement stores) does not come close to the quality of the older tools.
Some of my powered hand tools I do the same with, as a great deal of the "new tools" are, in my humble opinion, of inferior quality to the older tools. Case in point, I own an old corded 3/8" VS reversible drill that I have had for over 30 years. Chuck recently wore out, and I had to replace it with a cheap replacement chuck that is not nearly as good as the original, due to unavailability of equal replacement chuck. (Subsequently found source for quality chuck, which will get purchased soon and trash the cheapie.) Cannot find a new corded drill I feel is equal to old drill, which made this one a "no brainer".
If my cordless drill pooped out, I most likely would replace it with new, as newer cordless drills are better that the old drill I have now. They have more torque, longer life between charges, those key-less chucks (which I detest when using round drill bits) are a little better, which makes this an easy choice too.
There is no hard and fast answer to replace or repair, it should be evaluated closely by the user, and let your heart be your guide. If you do choose to junk it, you always have an option of recycling the old stuff - just put it on Craigs List, E-bay, etc., for someone who may need a part no longer available to make a repair they need, such as a drill that has been dropped and broken the plastic case. They swap out the good condition part with the broken one, throw away (or recycle for you environmentalists out there), and they are back in business! Just a thought.