Over my career I’ve written one specification book. It was by “accident” – my firm had taken a TI project for the city, and and even though we had not planned on putting together a spec book, when a client like that asks for one, you do it.
Furthermore our usual 3rd party spec writer was overloaded so it fell back on us. So I compiled the sections, had an epic editing session with my boss to edit all the selections and then handed off the chicken scratch to an intern to do the edits.
Fast forward a year and a half later and I have now reviewed about ten spec books, four of which are massive tomes for major new structures.
Day to day, you just don’t know what experience will be absolutely crucial to your future self. But you can tackle unfamiliar tasks with gusto. Most of the time I’m certain it will fade into memory, but occasionally you’ll be very grateful you did.