Japanese Burial

Why is a Japanese family grave sealed after 50 years and therefore, no new ashes can be added? we were told that a relative from the US who is Japanese cannot be buried with her relatives in Hakata due to this custom.

I've never heard of that custom. I think it's more of a "system" that applies to the certain grave the relatives have contract with.

But it sounds practical, and similar things do go on. Let's face it, you can't keep on taking care of ashes and bones of centries-old ancestors you haven't even met. They're not enough room either. Of course, many prestigeous families do that, but it usually costs them a great amount of money for maintenance, and it's those who are left alive that pay it.

In any case, most people in Japan don't bury "relatives" in the same grave. They just bury ashes and bones of direct children. For example, if a parent has 3 sons, the eldest son might be buried in the same grave, but the 2nd and 3rd son buy new ones. If the eldest son has no children, then that grave will be finished at that generation.

Do all relatives usually live in the same house? I don't think so. It's the same with graves. No hard feelings.

Never heard of that before either. Maybe its a rule specific to the temple or gravesite. Do you know the info for the place that they inquired with?

My family grave is located in a temple a whole day drive away from Tokyo and its been there for God knows how many generations. Noone in the family lives in that town anymore, but we visit there maybe once a year and pay the priest at the temple to take care of it.
As other people have noted, it may have to do with the contract for the particular cemetary. More traditional arrangement like ours usually have no such timelines.