All boosts last for three months. The accounts will have to stay in your server during that time period.
I cannot offer refunds because once the boosts are payed for, I can't just magically cancel them. I hope you understand. However, if there is an issue on my part, I will offer a refund or replacement.
I also do custom boost amounts (as long as they are an even number like 2, 4, 6, etc.)! Just DM me.