I have a 14.4V DeWalt that I've had for 10-12 years. It has worked great for my occasional use but the batteries are finally dead. I can buy new batteries but they are expensive, or I can buy a whole new drill/batteries/charger for less money with Christmas sales going on. A couple of off-brand batteries on ebay or amazon would be about $70, rebuilding my current batteries with new cells would be about the same amount.
Or I can buy a new 18V or 20V drill on sale for $100 or less. I'm real tempted to buy the new DeWalt 20V Lithium but I'm not sure about Lithium battery use in cordless tools. (I realize that cellphones and laptop computers are mostly Lithium.) A few years ago I bought a set of Rigid tools on sale at HomeDepot, and the Lithium batteries have been worthless on those from the start. The batteries supposedly have a lifetime warranty but they have enough loopholes that they get out of the warranty. So I have yet another drill plus impact driver and reciprocating saw that are worthless.
I would like to buy a new drill that I can count on to work for a long time, and have manufacturer support. I see DeWalt, Hitachi, Bostich, Milwaukee, Bosch and Makita selling drills that look similar, for similar prices. I'm not sure if any of these can match the quality of DeWalt, and I'm not sure if Lithium batteries can match the performance life of NiCad batteries even with all of their shortcomings.
I intend to find a way to get at least one battery for my old DeWalt 14.4V just because I can't stand to see it go to waste, and I'm going to continue trying to get warranty replacement for the Rigid batteries. But I could also justify buying a nice new drill with new batteries.
Another thing I've thought about- there are a few small drills on the market with 12V batteries. These would be advantageous sometimes around the house even though they won't drive the big stuff like the big drills. So another option is to buy a new 12V drill and get new batteries for my older big drills.