There is not a time limit per se.  The timing of who and when someone can inherit is determined by the order set out in a will.  For example, many couples execute similar wills, leaving everything to the other spouse.  They then include provisions that if the other spouse should die first, then their estate will pass to another heir... and if the heir is deceased... then their heirs.  A will can make other provisions... but the will, as long as it's properly executed, will control the timing and the order.  If an heir decides to refuse a gift, then then gift will skip to the next heir in line.  If an heir is known to exist, but for some reason is unavaible to recieve their gift, then the gift or inheritance can be held in trust until they are available to receive the gift.  How long it will be held will depend on the probate court.