Problem with pay pal subscriptions

I have implemented pay pal subscriptions (daily) for some service on site. But I have problem with time.

User pay for subscription at 10:30AM I receive IPN message save it to database and give user 24 hours to use service. When after 24 hours pass I want to give user another 24 hours to use service etc.

I tested this yesterday and next IPN messag开发者_开发知识库e I have received at 1:20PM today. This is more than 24 hours. But I can't let user wait 2 or 3 hours more for payed subscription.

I have option to give user 24 + 5 hours but I don't know is this ideal solution or it is?