Sure... I think the biggest thing is not so much whether there is bottoming out or the numbers... it's getting animals, bacteria, and plants, etc., soaking up nutrients and growing/stable populations... Whatever the numbers are they are... you just need animals and plants in sufficient volume and growth to out compete dinos, IMO...
For example, my tank has had nitrate between 0 and 2ppm and phosphate between 0.04 and 2ppm during the last five months or longer. The tank looks the same regardless of the numbers... The growth is the same... It's just whatever the levels settle in at they settle in at... The only numbers i would really monitor is alkalinity and PH. Keep alkalinity stable is the biggest thing and if PH is below 8 then use kalk morning and night or steady drip/dosing pump to both keep alkalinity stable and raise pH.
That said--i am sure we don't know everything about reef tanks and the "wild ride" could continue no matter what you do--even if perfectly... so patience is key and you've done amazing there!!
On that train of thought, if it was me i would add as many easy corals and macro and phyto into your system as you can or can afford... I have some gorgonians and digitata and easy zoos you can have here in a bit.. the plugs are still encrusting in the frag tank (that tank is new and no rock at all so slower growth).. those corals grow well and have tolerated abuse well. ..
I'll be transferring my 20 gallon tank corals and fish into a 50 gallon lagoon EXT in the next week or two.... tired of fragging corals every couple weeks.... That will technically be a "new" tank... But because the inhabitants (and light layer of SAND!) are established, i doubt i will have problems... we'll see...