Understanding index fillfactor
Free space within the table can be used to speed up certain kinds of updates on tables, do inserts faster by avoiding the need to extend the table, and make index growth more efficient.

If your table only changes infrequently and you don't mind reindexing it (or dropping &amp; re-creating the index) each time, that's totally fine. A fillfactor of 100 will save a little bit of I/O when scanning the index, and the spare space is no use to you unless you do inserts/updates on the indexed table.