Best lawn tractor battery

Rani, it's not the battery's fault. Any wet cell battery must be run for a length of time to maintain a charge. Our car batteries last a long time because we drive them often and a charge is maintained. Don't drive it for a while and it usually goes weak. Just like our lawn and garden equipment.
Add to that the lower amperage of the smaller battery and they don't usually last long.
I have seen some last as long as 7-8 years. 12 years is amazing or well maintained.
Leaving our lawn tractors out in the elements also does not help in battery life.
I have had my best service out of Interstate batteries. When I had my Small engine shop they were all that I sold. My customers were happy.