I'm considering a tapered retaining wall - L shaped. The 90 degree would be the highest point of approx 30" inches. The long side is about 50 feet long and the short end about 10 feet long. I plan to fill in the area and make it level for a slab that will wrap around an in-ground pool. I plan on doing cutbacks or deadman ties aaprox every 8 feet.

How long would this last? 40 years? I realize water run off plays a roll. I was going to fill with crushed concrete. The slab would be about 10 feet wide also L-shaped. Price is my concern so I selected pressure treated. Is that the best choice? The wall does not have to look pretty but functional. A foot would be very expensive for cinder blocks.

Any suggestions?

I'm not a contractor, but I did a lot of research on this for my own walls.
You might consider interlocking blocks such as Anchor Blocks (http://anchorblock.com/). They can be supported with geotextile fabric (http://www.tcmirafi.com/products/product_xt.html) for higher walls or greater stability.

According to their literature, you do not need a footer, but only a bed of sand or crushed rock, and build part of the first course is below grade.

All the information is available on the web; however, I hope a more knowledgeable source reads your note.

I was very happy with the walls I made, 4' high and 15 to 30" long, tapered.

Good luck.

The lifetime for presure-treat really depends on things like water in the ground, exposure to weather, etc. I used pressure-treat a6x6 RR ties around a patio, and much of it pretty much rotted after 15 years. The portion that is above ground survived much better. Also, if you cut any of the pressure-treat wood you leave exposed surfaces that are not as well protected - they will rot first. I ended up replacing the wood ties with pre-cast blocks, and they work much better and (in my opinion) look better too. One final note - be sure that the concrete slab does not come in contact with the wood - the lye in the concrete mix can destroy the wood in a matter of a few years.