I use a Battery Fighter smart charger, same sort of thing as Optimate. Don't like the idea of leaving a battery on charge unattended, so the charger gets plugged in & switched on until the charge light goes green, then switched off and perhaps moved to a different bike. In Winter, I try to remember to charge all of the bikes about once a week. While the bikes are in frequent use, the charger is rarely deployed unless it occurs to me one of the bikes has been sitting for a few weeks without use.
Batteries usually last for years. Kawasaki W800, bought 2014, still on original. XS650 still on the one I fitted when I bought the bike in 2019. Both are MotoBatt.