Hi @Michelle M
I actually have a use case that I recently did where I just used a smart campaign vs. a program. I had to create 2 outgoing emails in one campaign, but the leads for the recipients of the emails are in 4 different programs in Marketo. To avoid having to create 4 different emails in each program, I just created the 2 emails in Design Studio so I can easily access it. I created 2 smart lists referencing the leads from the 4 programs in the leads database, but the naming convention for the smart lists, campaign and emails are consistent so I can easily find them.
It would have been easier for me to just create a new program and have all of the assets in one place, but my boss didn't want it that way.