It sounds like you're not actually in LOVE with these Guerlains. I think you shouldn't buy unless you truly love the fragrance! Keep looking, I'm sure you'll find something that is more to your liking. Having a perfume you don't love just because it's from a certain house isn't worth it. Try other houses, other perfumes and see what's out that that you just can't get enough of!
I've tried all the Guerlains you mentioned. Shalimar just wasn't for me, Samsara didn't do anything for me, and Mitsouko was an olfactory offense to my nose. If you're interested in Mitsouko I recommend you DEFINITELY test before you buy. If you want Guerlain perfumes, why not try some of their other fragrances, and see if something else really makes you go "Wow! This is great!" I'm about the same age as you, and the only Guerlains I own are Champs Elysees and Cherry Blossom Fruity. While I don't really own any 'prestigious' and classic perfumes that get raves here, I've stuck to whatever I fell in love with, and I adore my wardrobe. I suggest that you just keep on testing lots of different things, and really only buy something that you know you truly love!