I'm considering buying/giving a Boost phone to someone who doesn't really need or use phone on regular basis. This would be for emergency etc. My question/concern is that I don't want to lose any credits if they go un-used. I understand that a re-boost is required at least every 90 days. Correct?

What's the minimum Re-Boost?

If there are still usused Boost credits, will they continue to accumulate?

It looks the Chirp Days, Chat Nights plan would be best for this type of user. Correct?

What are the gotchas? Any suggestions?