This sounds like the sin of presumption (presuming upon God’s mercy so that you can sin). Yes, I’ve done it (intending to confess even as I sinned instead of just not sinning). No, it wasn’t healthy, and I learned better while working to better form my conscience. I think I’ve confessed both sins (presumption, and the sin I committed while presuming upon God), but it was a while ago. I have no idea how many other Catholics do this. That there is a name for it indicates that I’m not the first and probably will not be the last. However, I think most people doing this know deep down that this is wrong, even if they don’t know precisely why.
I don’t really see purgatory as a ‘back up’ plan, nor do I know of anyone else who does (not counting children). I understand it more as healing I will likely need to be perfected for Christ’s kingdom, although if God gives me the grace I need to enter Heaven immediately on death I will be eternally grateful (what perfected soul would not?). The thought of suffering in Purgatory is not really frightening, as it is clearly a redemptive suffering. But I would love to taste Heaven while I am still here on earth (or Purgatory - redemptive suffering can happen on earth, too), and the way to do that is to draw as close to God as I may.
I’ve heard that meditating on Christ’s Passion is a wonderful way to curb the tendancy to persevere in sin and deal with it later. Each sin we commit is another burden He carried to Calvary. I haven’t really done this beyond praying the Sorrowful Mysteries, but hope to make more time for this in the near future.
Along these lines, praying a Divine Mercy Chaplet novena starting on Good Friday (ending on Divine Mercy Sunday) is a great way to recall that our sins come at a price, and that Our Lord paid it for us. “For the sake of His sorrowful Passion, have Mercy on us, and on the whole world.”
I’m writing these notes as much to myself as anyone, BTW.