We typically plan to arrive at charter base on Thursday, for a sleep aboard. We take that day to finish the provisioning and get settled on the boat, then depart Friday am. We like to return the boat on Monday which gives us 10 nights on charter. We've done this both in USVI and BVI and it has worked well for us. For BVI trips we also like to get to North Sound Friday night which positions us for Anegada on Saturday and Sunday night.
For May charters we normally bring the boat back on Memorial Day which saves a vacation day due to the holiday. I will say we hate getting on the plane the same day we get off the boat, so we plan an extra day after charter on island which burns that vacation day you saved but for us it's always well worth it.