I charge my LiPos in the evening after I have finished flying. LiPos do not loose their charge, so if you charge one up today, it will still be fully charged next week. DO NOT top LiPos off. This is one of the shurest ways of creating a problem with your battery. Get a fire proof container to hold the battery while it is being charged. An old army ammo box works great. NEVER charge a LiPo at greater than its rating (i.e.: an 800mah should never be charged at anything greater than 0.8 amps; a 1200mah should never be charged at greater than 1.2 amps, etc.)

Get extra batteries and charge them all at home. That way you don't need to waste time when at the field.