One rule of thumb is that you lower the dose immediately on any low # (nadir below 50, PS below 150, or slightly different #s depending on your comfort level), but do not raise the dose based on one higher #.
So if you go by that, if you lower the dose, you would hold at your lowered dose unless you see another low #, and then lower again. If the #s go higher after a couple cycles on the reduced dose, then you would consider raising the dose either back to where you were before, or to somewhere in between ideally.
Yes to what you said about #s headed down all day - if you see a late nadir, I would lower the dose. If he is too low to shoot tonight, you have options:
- wait and retest in say 30 minutes and shoot maybe 1.2 or 1.4 once he is over your no-shoot level
- if the # isn't super low (like say you got another 130), do a rising # test if needed and shoot a reduced dose like you did before
- if the # is super low (under 100 or possibly a little higher) and waiting til you get a shootable # isn't practical, skip the shot and pick up with 1.2 or 1.4 in the morning
But if you shot something like a 0.6 tonight, I wouldn't stick with that in the AM (unless you get a perfect PS). Most likely he would go higher overnight, and then you would go back to your trial dose (say 1.4 if tonight's PS is low) in the morning.
Generally I would say you want to hold a dose a few cycles if you are on a dose increase path, if you need time to gather more data, if you need time to see what a dose is doing (like the #s are wonky and you want to hold steady and see if things settle down), or if life dictates that you can't think beyond that dose right now.

When you have data on any given cycle though that is telling you fairly clearly that the dose is too high or too low, then I think it makes sense to adjust the dose as soon as you see that. For many cats that isn't the case, and for them, there is some need to hold a little steadier with the doses and see what happens.
But in any case you would almost always want to lower immediately if you get either low nadirs or PSs.