I recently read that as a rule the SAH parent shouldn't try to accomplish anything during nap time. I thought it was solid advice. It's the only break you get! Staying home may be somewhat mindless, but it's not easy.

Also, not having many words at 15 months isn't concerning to me. Similarly, my son only used a few words consistently up until his verbal explosion which happened around 22-23 months. Maybe me staying home with him "delayed" his language development in terms of him needing to use it, but he was still learning the whole time, and I consistently find myself surprised with the words and phrases he uses.