I want to plant young Mugo Pine "Wintersonne" into formal concrete containers, and I need a planter mix that can last more than two years.

In my Azalea and Rhododendron raised beds, I make a soil that is in the right pH range:
4 parts nitrolized redwood compost (sawdust)
1 part peat moss (to give acidic pH)
1 part turface hard fired clay (to provide a bit more moisture and higher mineral retention)
So far the plants appear to really love this soil, one year into the experiment. Does anyone see a problem with this mix long term?

I realize that small particle sizes are the enemies of drainage in a container. I would say that this mix is very bark-heavy and does not hold a lot of water, so I think it might work. The alternative is to use large pieces of bark, but then this does not have nitrogen added and I have to hassle with adding fertilizer to the entire soil mass as well as making sure to regularly fertilize it so that the decomposing bark does not turn around and kill the plant in a few years. I would end up with something similar to 5-1-1 mix, which everyone loves but honestly it is a very dry soil.

What happens to the nitrolized redwood compost when the original nitrogen fertilizer is used up? Does the redwood sawdust start to tie up nitrogen? Does that argue for a need to fertilize this bed more often?

Last photo is the Azalea raised bed with the soil mix I have described.