You have up to 24 hrs @ 75 deg. You should at least wait about 30 min. If you go past 24hrs you can shoot another coat of base and then clear. The best thing that I have found is to shoot a coat or two of intercoat clear after the base coat. That way if I go past my time frame I can scuff the intercoat with a red pad then shoot clear. The intercoat clear will also protect the base coat before you clear. You can not sand Metalic, Kandy or Pearl base paints or you will scratch it and it will show.