Never heard of lubing a bullet. WTH?
As far as magazine springs: They wear out due to use, not from the designed compressed state. If you over compress the spring (like putting more rounds in the magazine than intended for), you'll damage the spring right away. But just from keeping the magazine full of rounds to the designed limit you're fine. The magazine spring will "wear out" due do constant compression and expansion, fatiguing the metal. In short, a static, compressed state magazine will last a long, long time. A magazine in constant use, at its design limits, will last a long time. A magazine miss-used, won't last nearly as long.
Edit: If the magazine is good for 12, fill it to 12. It'll last just as long with 11. If you fill it with 13, you over-stressed the spring and its weak right away.