I flew several of these flights in 2016 and was surprised to see good availability this year until late May. You must book with the connection in SLC to get 6,000 miles.
Same day turns available. For example Wed., April 19, dep 6:00am, back to Orlando about 11:30pm. Austin is small enough that you could zip to get fried chicken, Asian stir fry, maybe even Salt Lick BBQ within 30 minutes.
If you want to enjoy the People's Republic of Austin overnight, Tuesday outbound is cheapest, 6:00am flight arrives about 1:45pm, Wednesday afternoon departure abt 2:40, back in MCO abt 11:30pm.
Similar arrangement and fares MCO - DFW totaling about 5,500 Rt, again through SLC, but DFW is much less pleasant than AUS.
Another plus, last year AUS - SLC and SLC - AUS were always commuter planes. This year every thing I've booked is on A319s or A320.
Happy New Year and safe travels everyone...