As for protecting terminals from corrosion there are two schools of thought:
1. Some type of grease
2. some type of lacquer or other sealant
They both work about equally as well.
The problem with grease is once you put grease on the terminal, you're pretty much stuck with grease from there on out. Grease is cheap, readily available and easy to re-apply.
The spray on sealants are a little more permanent and a little less messy but you have buy the stuff.
A spray can of sealant for battery terminals will last for years and the stuff is good for weatherproofing other things as well.
When I get a new battery, I clean the terminals and cable ends (even on a brand new battery) assemble everything and spray the connection with sealant; usually two coats.
I am also a HUGE, HUGE fan of battery tenders. The little extra expense of a battery tender (or a small solar charger if stored in a remote location with mains power unavailable) is worth its cost several times over. A 110 volt automatic battery tender is a one time expense and it will pay for itself in one battery replacement cycle. The electronics for those devices have become inexpensive and durable.