Laptops get abused. A 3 year warranty is a must for a prime machine. Refurbished laptops should also have at least a one warranty. Extended warranties are often available, but don't pay much for one. If the warranty is poor, don't buy it.
Batteries only have a one year warranty because of the charging cycles.
Many manufacturers offer the same machine in a one year warranty version for a little less than the 3yr warranty machine. The cost difference is very small - certainly not worth the poor warranty coverage. Lately the trend is to offer the machine with a one or two year warranty and charge the customer extra for the three year. This might be OK, but bet your final price with the three year coverage. Only buy the three year machine.