You don't have sticky lifters, you have leaky lifters. The check valve is not sealing, or the lifter internal parts have a bit more clearance, and either or both will allow leakdown over time. It is normal. It won't hurt anything.
If you insist, you can do some of the above tricks to disable the injectors and/or perhaps place a switch on the relay power side or the power to the ignition module to disable spark, etc etc etc etc etc.
I would ignore it. I have a tap that comes and goes, depending on how long between running the engine, and which cylinder happens to have a valve open when I stop.
I would sooner have lifters that were a bit too loose internally, and tapped now and again, than lifters that were too tight, and held the valve off its seat... causing the valve to burn up and cause more problems.
I'd suggest leaving it alone, starting more frequently, or removing the offending lifter and replacing it with new. You might find that a new lifter has the same problem, you never know. You can remove them and apply external pressure to simulate a valve spring, and test how long they take to collapse, and how much pressure they withstand before collapse, but it's easier just to ignore, or remove clean and re-install, or replace with new.
The oil viscosity likely won't have much effect as the leakdown is so slow and over such a long period of time.
tom,
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