ante is right, faster charging will shotren the life of ur battery but i can give some tips for better utilisation if the sla is not dicharged below 20 % DOD (depth of discharge) u can recharge it from 20 %dod to 80 %dod in around 2 hours . the first 20 % (from 0 to 20) and the last 20%(80 to 100) of the battery take longer time to rechgarge because of the chemistry of the battery ( around 2-3 hours each) make sure u are using a good quality smart charger . hope my answer helped u . :)