Galliano-Shelf Life?

I'm hosting a big cocktail party in a couple of weeks. One of the cocktails I plan to serve is the Harvey Wallbanger. It's been years since I bought Galliano...and I'm surprised how pricey it is...especially since I don't need a large amount.

Well guess what? I have about 3/4 of a bottle of Galliano in the back of my liquor shelf in the pantry. However, it may be old enough to be considered an antique. If I had to guess, I'd say it's probably 15 years old!

It's been so long since I've had a Wallbanger, I don't remember what Galliano is supposed to taste like! I took a sip...still very sweet. No crystallization or debris in the bottle...pale yellow color. It's been stored in a dark place this whole time...upper shelf, so it may get a little warm in summer.

What do you think? I can I save myself another $35 and use this Galliano? I don't want to seem like I'm just being cheap...I hate to throw out something that well work just fine.
But budget is a consideration somewhat too...and I really want to serve Wallbangers (I'm doing 2-3 other cocktails and lots of food)!

Thoughts? Thanks!
rowjo