They can take quite a while to charge, but you don't need to wait until they're fully charged to use them. They'll actually live longer (more charge cycles) if you don't fully discharge and charge them every time. It is, however, a good idea to charge them fully periodically and then check the voltage...they should be right around 4.2v fully charged...if a batt begins to vary from that it's time to take it out of service.
Also, if you happen to be unfamiliar with Li-ion
batteries in general, it's a good idea to read up on them a bit...there are some risks with them that are good to know about. For example, it's a good idea not to charge them unattended, and to never leave them in a charger after they're fully charged...cheap chargers will often trickle charge batteries once they're "full", and with Li-ions trickle charging can and does make them burn, violently. Apologies if I'm telling you something you already are aware of...but better safe than sorry, as they say.