What does it mean to celebrate the longevity of Xianghai House?

It means that the flower year symbolizes good luck, and the next sentence should be "adding money to the sea" instead of "longevity", which is taken from an allusion.

Legend has it that there are three immortals on Penglai Fairy Island who live longer than each other. One of them said that whenever he saw the sea on the earth turn into a mulberry field, he added a branch to the bottle. Now there are ten rooms stacked with chips. This is the legendary story of adding chips to the sea house

This should be a birthday greeting.

Hope to adopt, thank you.