On my last 3 ncl sailings, I've had my daughter wait until midnight going into day 2 and we've received the discounted rate and I'm happy to save those few dollars. Yes, she couldn't use any minutes before midnight, but she was ok with that. We always board around 11am, so she has until sailaway to go crazy and then dinner and entertainment keeps her busy until midnight. Last year on Joy, the first 2 had the 150 minutes, so she used mine on that first day before midnight and then she upgraded hers at 12:01am.
We're sailing Joy again this summer and will employ the same strategy. It's not a huge savings, but I like it anyway.