The flanges are fixed, and the tubes merely slide over the flange and fit with friction alone. Because our table is 6 foot long, and heavy, it is helpful to have 2 of us lift the table and remove the posts. We then place the alternative posts on the floor flanges and replace the table top. Takes about a minute as long as we are on the same page.
We have found that the aluminum paint scratches easily, so we plan to spray them with clear coat. Alternatively, we could repaint them regularly depending on use. For the price, we'll deal with the maintenance.