Personally I find thread basting to go a lot quicker than safety pins. It's absolutely easier to take it out!

I don't like to thread baste,and safety pins are hard on my hands, even the curved quilt ones. So I spray baste. Left one for over 8 months and it was still stuck together when I went to quilt it. I always wash my quilts after they are done and the spray baste comes right out. Use a good one though.

I wouldn't chance leaving pins in that long. Now would seem like a good time to try out your basting gun!
peace

I would be leery of leaving the safety pins in for that long too :D:D:D