I've recently bought a lithium battery for my Vee.
It certainly does whizz the starter motor with a lot more oomph. The battery weighs almost nothing.
Most batteries that don't last more than 1 or 2 years probably weren't charged up properly before the 1st use.
EVEN IF the instructions say "Use straight away" or "No need to charge" YOU DO need to trickle charge the battery for at least 12 hours prior to fitting it to your bike (Do not put it on high charge for 12 hours!!!)
This is to condition the battery - it will make the difference between a battery lasting 2 years to lasting 5 years! I got this information from a radio technician who uses a lot of bike style batteries and he did his own tests, his results were for his own use and not for any battery company. He knows a lot more than me and for once I paid attention