Hi Jamie,
We log form comments in interesting moments and as completed activities. Yes, interesting moments do archive, but in our system it is longer than 90 days. I put in a request with Marketo to wait for a year before archiving our data, so that might be why. Even if it did archive in 90 days, I love having the notes in interesting moments. It's so clear to sales reps what happened and when.
If they need to go back for older comments, they could check the activity log.
Delinda