IME it's beneficial to rest when you feel tired from riding. That said, not always. Sometimes it's beneficial to ride when you feel tired from riding. It's not too difficult to figure out which is which. Right now, you're gradually increasing the distance you're riding. Maybe you have a plan in mind for that. So you go out riding, wanting to ride some certain number of increased miles, but partway through, you feel like you can't pedal as hard as you did the last time. You're going slower and nothing to be done about it. In that case, pedal on home comfortably and take the next day off. Otherwise, keep going.
The usual advice on incrementing ride length is to keep track of your weekly miles. Try to increase your weekly total by ~10%/week. However, like compound interest, after some number of weeks you'll find this gets out of hand. So then cut it down to 5%. Another thing most folks do is to ride one longer ride each week, usually a weekend day, and then shorter rides the rest of the week. After a while, you can keep pushing the weekend ride to get longer, keeping the weekday rides about the same.
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