Transaction log backups cleaning
I would play it safe and delete files older than three days, a week, two weeks, what have you. You never know when management will run to you saying someone accidentally deleted data yesterday or before the weekend and they need to restore to a point in time. Make sure you retain enough data to cover all of those possible scenarios, and if you don't have enough space, buy more - it'll be much cheaper than being up the creek without a paddle, trust me.

Also, make sure you are testing the ability to restore your backups before deleting older ones, and validating they're consistent. You suggested that you would feel comfortable deleting yesterday's logs based on the fact that last night's backup executed successfully. That the backup executed successfully isn't enough. You could be backing up corruption for a week, and how would you know unless you actually tried to restore?