Respect people’s time. With that been said, don’t take too long to respond to your messages. I believe that 48 working hours (which is 2 business days) is the maximum amount of time that you have to follow up with someone before you begin to appear like you do not care or you think you’re too important.
We are all busy people, and often, we are pulled in a lot of directions. If you’re so busy, your reply can be as simple as “I am backlogged on emails right now, so I’m reaching out to let you know that I saw your message and I will get back to you as soon as possible. Looking forward to connecting soon.”
Treat others the same way you would love to be treated, except those who only reach out to you when they need a favor from you, and never bother to check up on you in between favors.