It surely can be an excellent source of spiritual guidance to spend time reading their lives, if you have the time. Already, you know how much you were inspired by St. Faustina. The mind becomes a virtual data base of “how-to’s” and just when you most need an instruction, the Holy Spirit can bring to your memory an example of theirs that might just fit your situation.
Another beautiful benefit is that it keeps us humble when we see how far we are from their holiness, while giving us encouragement to keep trying to ‘win the prize,’ as St. Paul worded it.
The only caution I would make is not to follow some of their penances without specifc spiritual direction. If you are familiar with St. Catherine of Siena’s Dialogue, the Lord gave her detailed instructions on the use of penances - - many of our own choosing are not spiritually beneficial.
I like the simplicity of St. Therese’s Little Way, and the Resolutions of St. Gabriel, which are quite similar to her thinking.