Actually, you can boil bass/guitar strings when they are new.
I haven't heard much about boiling bass strings to revive their sound, as I don't play much bass.
But I do know that if you boil guitar strings and dry them completely, they will be instantly "broken-in"
When you first put on new guitar strings, it takes time to break them in. They are naturally tense right out of the factory, and for a day or so, the strings will constantly go flat out of tune. This means the string is gradually loosening up. Eventually the strings will be broken and and will stay in tune, as long as your guitar keeps up.
But if you boil your strings, it will relieve the tension in the strings, and will be instantly broken in.
I believe it was Van Halen who used this little trick regularly, on all of his strings.