Agreed, if the rollers are good and tight, roll smoothly and do not have visible wear you definitely can disassemble and inspect the plungers and clean them out. Hard to determine if the check ball is holding by inspection though.
Although it's somewhat of a common practice, I'd not recommend adjusting the preload out of spec. This is just compensation for another problem, essentially turning a hydraulic lifter into a solid lifter.
Bottom line, when you get lifter noise, generally the solution is to install a fresh set. They're not too expensive and with adjustables is a fairly quick and easy job.