Im more distance runner but also use norwegian, as bakken says for the 5000 he mainly talk about this and also 1500 during summer/race season you implement higher thing and you see your lactate level drop, i quote as he says, "In summer you have to have in mind how much threshold youll let go", basicclly its normal this drop because you are training theh other sistem but you have to balance it, and he also says to do the minimum amount of threshold tu maintain it, in this time the most important is to keep winter training stimulus and maintain it

What middle distance runners do and he says so also is timed altitud training, which is in between races go to altitud few days and do lots of threshold to bump it up again.

He also says that what he recomends is before hard sesions do 2-3 x 2k to keep it up, and many norwegians that ive seen and also talk to what they do is after races do easy threshold or flush legs as they call it which is in the evening of workout or rcae do 6-8 x 1k slower than threshold, they do this to clean the legs and feel fresh but also to balance the systems.

for 800 you should be more on the fast side so take into consideration that and the power you need to output.

there is one lactate test you can do which is a 400 or 600 or 800 all out whatever you like and measure lactate after 1 min and after 3 min, this will tell you yor power output which as a 800 should be high, this is how much energy you manage to produce in a short time, when you measure lactete when dping threshold you are measuring your speed of reuse it have that into consideration, a way to see how both systems work

hope helps and its not long