I have seen something similar and it didn't end well. Though the partners brought very different things to the table. People also invest energy in cycles so i

I have seen something similar and it didn't end well. Though the partners brought very different things to the table. People also invest energy in cycles so it could just be "founders doubt" or "burnout". Make sure you are both still having fun...and use all of the lessons you can from dating and marriage. This could be like the business version of "seven year itch".