2 years ago I have left my 9 month old son at his grandparents house (also where my sister and her hubby live) for a week to go down south on vacation. Again in April I will be dropping my 2.5 yr old son and 1 yr old daughter at their house again for a week!
If tehy are with trusted, capable family/caregivers, why not? Everyone needs a break and I will miss them like crazy, but I thinks it is good for everyone.