air comes out the windshield defrost vents most of the time (99 %), but, occasionally it will come out dash vents. I replaced a couple vacuum hoses going to firewall, so, there is vacuum there. Have there been hose problems going to air control panel?

What is your question?

We turned the air on a couple days ago and the air came out the dash vents after only coming out defrost for several months. It worked until car was turned off. Then next time we turned it on air came out defrost vents again. Been doing this at least 5 years. Bottom line---Air comes out defrost vents most of the time. Like I said above, I replaced a couple bad hoses going to firewall, so, there is strong vacuum there.

What makes this problem better or worse?

doesn't seem to be any better or worse.

How long has your 1993 Buick LeSabre had this problem?

5 years