The Umbrella Plant loves to be growing in moist soil for really good growth to occur, but it will certainly accept a level of underwatering, so if you forget to water it for a week or two after the soil last dried out, it should forgive you. It’s not so forgiving of being overwatered however which can result in root and stem rot. Pour any excess water collected in the drip tray away to avoid this problem. In general the bigger the plant the more water it’s going to need except when it becomes inactive in Winter, at which point just water enough to keep it ticking over.