A great travel lens stays in your bag for a decade, capturing sharp shots in low light and making every trip look like it had a crew behind it. Buying the right piece of glass the first time means you stop wasting money on upgrades that barely move the needle.
Wait for manufacturer rebates before you pull the trigger, since camera brands drop prices by a couple hundred bucks a few times a year. If a newer version just dropped, look at last year's model instead, because the optical upgrades are rarely worth the extra retail markup.
That 18 months on the Citi Simplicity® Credit Card is a firm deadline, not free money, and if you leave any balance sitting there when the clock runs out, deferred interest or standard rates will kick in hard.