In an online survey of 647 young adults, more frequent texting and the sense that a partner was responsive during text conversations were associated with greater relationship satisfaction among participants in long-distance relationships. No such association was found among participants who lived near their partners. These are self-reported data: they do not prove that messages themselves improve relationships or tell every couple how often they should text.
Try agreeing on what helps each of you feel connected and what starts to feel tiring. For example, you could set aside time for a more substantial conversation while giving each other space during the day. It can help to ask not only “Why didn't you text?” but also “What kind of contact works for you right now?” Distance creates practical challenges, but closeness is not measured by being online constantly. Sometimes reliability means clear agreements and room for each person's own rhythm.