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How does a ping-pong ball stay afloat a column of air when there is air supply at the bottom?

Basically, I have a ping-pong ball and an air-inverted vacuum (blows out air instead of sucking in air). The air-inverted vacuum is on and the tube connected to the vacuum is blowing out air upward (showing that the tube's exit hole is pointing updwards). I put the ping-pong ball about 2 feet above the tube, and it stays floating in mid-air for approxiamately 10-15 seconds. After 10-15 seconds, it stops floating and drops. My question is how does the ball stay afloat in mid-air let alone for a period of time? How come the ball was able to stay suspended in the air column?

first, let's talk about why the ball stays up.
when air is moving past a surface, the air pressure on that surface is reduced.
so, in the air column, when the ball starts to fall out, then there is more air going past on the side near the middle of the column, which reduces the air pressure on that side, and the ball is light enough that that little difference is enough to draw the ball back to the middle of the column.

if you were to google "ping-pong ball" "column of air" you'd get several hits, including:

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there is also a famous parlor trick.
take a small piece of paper, maybe 2" x 3".
bend the ends down so that there is a U shape, with a 2" square bottom.
turn it upside down on a table, and try to blow it over.
when you blow under it, you'll notice that it pulls the top down tighter to the table.
what you have to do is blow over the top, which "sucks it up" and will flip it over.

as to why, after 10-15 seconds it falls, it shouldn't.
unless, of course, you've turned the vacuum off.
or there is a cross wind that blows it out of the air stream.
or there is something else that you've not told us.
if you leave the vacuum on, pointed straight up, then the ball should float there forever.

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