I agree with both Matt and Adam here. The default boundary action profile is very good for most locations. That being said, in places like what Adam describes, where one is all you can get, the LS can and very often will get a good solution. The PPK will, if given enough time and with probably at least 2 different PPK session will then "validate" to you, the user that you have a good coordinate.
The LS and it's many, many adjustable settings is all about the user getting a "feel" for what it's doing and setting up your own personal profile accordingly. Matt is correct in that when in canopy the LS will almost never attain a full 6 engine fix, but that's not necessarily needed to get good tight reliable data. From our 2 years of use, the engines are, for the most part, weighted from #1 (the quickest and usually first to fix) to #6 (the last and most difficult to fix). Now, most times in the woods and under canopy, when we are collecting a point, we see between 2 and 4 engines fixed. It will most always include engine #1, but the other one to three that it will be using will be a mixture of engines 2 through 6.
Bottom line is, if your profile is set to collect for a minimum of 180 to 240 seconds and the LS completes all three phases of the RTK process, you can almost bet your last dollar you will have a good coordinate.
Again, that being said, we've had a ton of points, as Adam describes, that just won't finish either phase 2, or most likely the phase 3 validation. Still there's a very good chance you have a good coordinate here, it just depends on the data stored up to the point where you "stop" and store the point. If there's more than 240 seconds of separation between the epochs in the group it's an extremely high probability the shot is good.
I've stopped and stored these many times. After I do, I always "reset engines" while still on the point, hit start again and watch the "distance to last" white box and as soon as I get a few epochs that give me 0.03'/0.05' kind of numbers, I know the last shot was good. Then, usually having a PPK point collected, process that back at the office and most likely will get another good check.