Do long-time-pending transactions due to low fee ever cancel/drop by themselves?

I had a small amount of some ERC20 token in a wallet and spending the "recommended" amount for the fee would've been half of the value of what I was sending. So, I lowered it to 10gwei (around $2) to see if it ever goes though. It's been 4 days now and it's still pending. I'm not in a rush or anything, but I'm wondering what happens if it never goes through, does it eventually drop out or do I need to do that not-very-intuitive manual cancellation thingy?