I have a question regarding Lowe's and Walmart Discover - when do you count it being 4 months? From the date you were approved for the card, or from the first statement date? TIA!
From the 1st statement date or from the last CLI - whichever is later.
If you call the underwriters instead of using the automated system you might get one sooner. But I recently tried that and it didn't work. I was afraid the direct underwriters' line would soon fail due to the CB effect so I called a week early on my Lowe's card - DENIED. A week later (4 months + 1 day from my last CLI) I called back and was instantly approved for a HUGE increase.

IMHO it's better to wait 4 months + 1 day between requests unless you have a very good reason not to. There's a better chance of a CLI, a good chance it will be a bigger one, and less risk of unintended consequences. Of course when you do call you should shoot for the sky.