Ntrogen-when to restest soil?

    My new beds were low on nitrogen and phosphate.  I added organic blood meal and bone meal; then I read in these forums about dilute urine.  Before I enlist my husband and son (easier for them!), shouldn't I retest to see what the level are now?  How quickly does it take for blood and bone meal to take effect?  Can I use the dilute urine for a quick boost on top of the slower acting (I assume) blood and bone meal?
    I tried to research this in books and online.  I found a lot about what to use and how to use it, but nothing about timing for retesting.  Permies beats Google anytime.
   

Nitrogen, in general, is highly mobile in the soil. Rain/irrigation washes it deeper, plants cycle it up, and soil biology is constantly circulating it. If your plants are growing well and aren't either growing long and leggy with flimsy stems or turning excessively dark green and suffering from fungal pressures then your nitrogen levels are not too high and adding dilute urine probably won't hurt.

Phosphorous is much much less mobile and on a large scale people tend to test their P levels every 3 or so years.

Huh. My broccoli seedling's leaves were turning purple, which caused me to test my soil;  do I just assume the N level has risen to a sufficient level?

Wait a minute....I think I get it. if the plants look good, don't sweat it?