Most hybrid batteries are warrantied for 100,000 miles, but can be expensive to replace when the need arrives. It depends on the materials used in the battery itself. Lithium batteries will tend to last longer and go farther than conventional cell batteries, and will be lighter. When shopping for a hybrid car, remember to talk to dealers about the types of batteries needed by your vehicle. You may be able to use this as leverage for lower prices.

It's hard to answer this question because new batteries are being developed all the time. The cost of batteries was a huge issue when hybrids started selling in larger numbers, especially because the batteries wore out in just a few years. However, hybrid vehicle batteries have already improved considerably, so replacing your batteries shouldn't be a huge deterrent from buying a hybrid.