If you're into buy high end competition (80c+) lipos and serious about longevity, then I would say no, don't charge the packs the day before. Typically packs like these are encouraged to be discharged a couple hours after being charged. But if you're into buying cheaper (30c and less) lipos, then charge a day before if you want. But I wouldn't leave them fully charged for longer than a couple days.

hers a link to how i think lipos should be treated.http://www.promatchracing.com/faqs-dandd.php