[HondaDustR]

Not necessarily. Even if the oil drains down, they will usually pump back up once reinstalled and run. It just helps keep them full of oil, as extended runing with them "flat" can kill them. The round part that contacts the valve stem is the piston and should have little to no travel if properly filled with oil. If the oil drains out from extended sitting around or if the piston or check valve is worn and not sealing well, the button will feel soft. Sometimes you can get them to fill up and harden up by soaking in oil and pressing the button while submerged, often times they will just pump back up ok on their own once the engine is run, and sometimes they never do even when run because the check valve doesn't seal and/or the piston and bore is worn. The last case will give you the loud clacking of a collapsed lifter and it should be replaced. If they were quiet before, they are probably fine. Just store them in oil until reassembly. They will not instantly be killed just by sitting out of oil for any length of time. It just helps them stay full so they don't clack from needing to pump back up.