Hi there. I teach World Religions (and other philosophy classes), so this is my area of expertise.
Some religious traditions are more open to being practiced along side other traditions, while some have beliefs that demand exclusivity.
In Hinduism, for example, there are millions of gods… all of which are a part of the Supreme God. This logic can, and has, been extended to the gods of other religions.
Likewise, some religions pair together quite nicely, like Buddhism and Shinto or Taoism and Confucianism.
There are also ways in which some religions might have some common ground. You can apply some Buddhist ideas within your Christianity, depending on what those Buddhist ideas are. On this, see Thomas Merton’s work on Zen, or DT Suzuki’s work on Christianity.
As to practicing multiple faiths being a sign of maturity… I think it’s more that friendliness to ideas outside your comfort zone is the mark of maturity here. This can include atheism too. Someone who genuinely wants to understand other perspectives is going to walk away with at least a few ideas they can affirm.
Ain’t a bad idea.
Round about 10 years ago I lived alone in a little cabin in the woods. I didn’t have much in the way of money, didn’t need much of it either. Wood stove, books from the library for entertainment.
Shit, I was way calmer and happier when I lived in the woods.