At the last place I worked at with unlimited PTO where they were pretty friendly toward people taking time off, we started talking about a more employee-friendly policy that communicates that intent. Similar to what certain financial institutions have: a minimum PTO policy. Like you have X amount of weeks you have to take each yer. After that it's unlimited. It never was put in place before the company went out of business, but it's something to think about.

My current and next job I'm starting soon have fixed amounts of PTO separate from sick days buckets and I'm fine with it. I'm the type of person who always uses what he's given and it's just easier (for me) not having to do the guesswork.