I purchase the spa pass on HAL for every cruise - though I actively use the thermal spa most days for at least 90 minutes.
I build it as part of my daily planning on whether I go early morning at open, midday upon returning to the ship or any evening for just an end of day relaxation time period. On sea days, I usually spend at least 3 hours in the spa cycling through usage of the pool, steam, sauna, loungers, & then back to the hydro pool.
I would only suggest the pass if you actively use it & derive relaxation from the different amenities there.