Can you still charge with the Pronto charger or do you just charge using a std battery charger?

My batter allows the pronto to be used for about 1 evening before needing a recharge. I have my backlight set to only 6 sec and I am using IR only. Does this indicate that I need a new battery?

I bought it used so I don't know how well a new battery should perform. With a new battery how long can you go between recharges? (hours, days, weeks, months??)