you can manually set charging algorithms in your laptop. stop charging when battery is 95% and start recharging when the battery is below 70% or something. this will mimic normal battery charging and discharging cycle while giving you the option of keeping the laptop charged for emergencies.
trying to charge the laptop to 100% while using it is the biggest cause of battery life degradation.
for T-61 lenovo
Control Paner - Power Options - Power Manager - Launch Power Manager - Battery Information - Battery Maintenance