It looks like you've been given good info from some of the members above.
One of the best resources I have here at home is THE COMPLETE BOA CONSTRICTOR by Vincent Russo. Soon, I will have the second edition and from what other members here have told me it goes even more in-depth than the first book.
Vin Russo and his friend Gus Rentfro are very well versed in boa constrictor care in captivity and both have done extensive field work.
You may benefit from owning a copy the new book, or reading anything of the internet written by Gus Rentfro regarding proper boa care.
It is not normal behavior for a boa to soak constantly or even for long periods daily. That behavior should be sending a message that something is off. It may be husbandry, security, or mites.
I'm hoping you can get things dialed in.
Good luck.
