All depends on the timeframe you're talkin about. If it's just a couple months I wouldn't worry too much about the valve springs. Now if it's several months to maybe a couple years, yeah, take the rockers off.

Anyway, I used to have to preserve my engines when I went off to deploy for 6mos every year. I used my expereince with aircraft preservation & a couple other tricks & never came back to a damaged engine.

*Drain the carburator, pump, & lines of all fuel. Getting a little light machine oil into the passages where any check balls is a good idea to prevent them from freezing. Also good idea for the accelerator pump.
*remove spark plugs, & turn engine over by hand while spraying all around in the hole with light oil. Some folks just use WD-40, it works well enough but for long term something that leaves a heavier film might be better. Replace plugs.
*take off the distrubutor cap, clean it & the disty out and spray with WD-40
*change the oil in the engine
*spray the outside with a light machine oil, just something that will leave a coating on the inside.
*get a couple large packs of dessicant & put em on top of the engine to absorb moisture
*get a couple large trash bags, cut them open on one side so that you can completelt cover the engine. Seal it shut with duct tape & ensure all holes are closed. Just remeber to check it every now & then to be sure there are no openings & it should be good for a very long time.

the longest I let an engine sit in this manner was 7 months with no evidence of corrosion anywhere. I have another that I managed to aquire an airtight shipping container & kept it preserved for about 2 years, took it out, put the external parts on (I shared some parts between 2 of em), & fired it up.