Currently I'm still concentrating on adding to my lens collection as quickly as I can without upsetting my wife. My next purchases will be either a 100-400 II or 300 2.8 II. Probably at least 6 months off since I'm currently in the dog house...
You know the "dress in the closet" trick, don't you? It goes like this:
1. She buys a dress she's been wanting for a long time.
2. Instead of saying anything about it, she puts it in the back of the closet and saves the receipt.
3. Six months later, she wears the dress to dinner.
4. You say, "Where did you get that dress? Aren't we saving to replace the carpet?"
5. She says, "Oh this old thing? I've had it for months. You haven't noticed?"
6. You say, "Nope. I've never scene it before."
7. She digs out the receipt and says, "See -- I've had it for a long time. I'm surprised you've only just noticed me wearing it tonight."
8. Not to be in the doghouse for "failing to notice" months earlier, you say, "Sorry honey. You look amazing."
Should work with lenses, too.
The hard part will be not using the new lens for six months!