The question of lube or locking compounds seems to be a split issue. Some are in the camp that likes the thread lube to then dry to a soft locking "glue". That includes the boiled linseed oil that hardens after a week or so and apparently Spoke Prep that I thought was just a lube and any other locking agent.
Then there's the oil and grease camp. I'm in the oil and grease camp. Out of the dozen or so sets of wheels I've either built or rebuilt I've lubed all of them with a "soup" of grease with just enough mineral spirits in it to thin the grease to a thick oil consistency so it'll flow around the nipples. I dump the nipples in and swish them around and wipe a smear on the threads of the spokes as I install the nipples. The mineral spirits dries away over a few days to leave a thin film of grease to keep out water and prevent corrosion. Over the years the wheels need the odd tweak here and there but this is highly variable and I'm pretty happy that it's due to fair wear and banging around rather than the spokes actually coming loose from cyclic loading making the nipples creep. I DID have a couple of spokes come loose on me with one wheel but I chalked it up to poor tensioning on my part. It was fixed and the overall wheel tuned back up a couple of years ago and it's been fine to this day.
On the other hand lots of folks use the Spoke Prep or linseed oil with good results as well. So really it comes down to YMMV. I like my grease method not only for the lubrication and water repellancy but also because 5 and 6 years down the road I can still easily tweak out a bit of runout without the spokes binding and winding up.