In some ways they are more "forget about it" than lead acid -- lithium battery life is measured in cycles, rather than time. Your lead acid battery will be dead in 5 years, but your lithium batteries can last for 5,000+ cycles, even more if the cells are intelligently discharged.

As for cold temperatures -- less current can be drawn from each cell. In those cases, you can add more cells to still perform adequately in the cold. And this may even fit in the same form factor as the existing lead acid battery, because lithium batteries are physically smaller.